and modifications will simplify the process for extending the LOV.
    The FAA does not agree that establishment of an LOV for a future
airplane model should wait until the high-time airplane approaches its
design service goal. As discussed previously, establishing design
approval holder compliance dates that are a function of when high-time
airplanes reach their design service goal would introduce a level of
complexity and uncertainty to the requirements of the operational rules
that is unnecessary and inappropriate.
    One manufacturer is already employing the concept of establishing
LOVs based on the fatigue knowledge base available through the
certification process. Airbus has already included an LOV in the
applicable Airworthiness Limitations section approved by EASA for all
of its models with the exception of the A340.
4. Operational Rules
    For airplanes whose type certificate application is made after the
effective date of this final rule, LOVs must be established by the date
the certificate is issued or the date specified in the plan approved
under Sec.  25.571(b). The LOV will be included in the Airworthiness
Limitations section of the Instructions for Continued Airworthiness and
will apply regardless of how or by whom the airplane is operated.
    As discussed above, the FAA may issue a type certificate for an
airplane model before full-scale fatigue testing has been completed. In
that case, the Airworthiness Limitations section of the Instructions
for Continued Airworthiness must include a number equal to \1/2\ the
number of cycles accumulated on the fatigue test article. Under Sec.
91.403(c), operators may not operate these airplanes beyond this number
of cycles. Once the fatigue testing is completed and the LOV is
established and approved, operators may revise this airworthiness
limitation to include the LOV. This LOV will be higher than the
airworthiness limitation specifying \1/2\ the number of fatigue test
article cycles.

H. How to Set LOVs

    Section 26.21(b) of this final rule requires design approval
holders to establish an LOV of the engineering data that supports the
structural maintenance program. This LOV corresponds to the period of
time, stated as a number of total accumulated flight cycles or flight
hours, or both, during which the design approval holder is able to
demonstrate that WFD will not occur in the airplane. This demonstration
must include an

evaluation of airplane structural configurations and be supported by
test evidence and analysis. If available, service experience, or
service experience and teardown inspection results, may be added to the
test evidence and analysis to provide additional substantiation. The
service experience and teardown inspections must be of high-time
airplanes of similar structural design, accounting for differences in
operating conditions and procedures.
    The NPRM proposed in Sec.  25.1807(b) [adopted here as Sec.
26.21(b)] that holders of design approvals for existing airplanes
subject to the rule be required to evaluate airplane structural
configurations to determine when WFD was likely to occur for structure
susceptible to multiple site damage or multiple element damage. The
results of the evaluation were to be used to support establishment of
an initial operational limit (now the LOV.)
    The Boeing Company and industry representatives on the AAWG
commented that proposed Sec.  25.1807 would require an ``evaluation''
that is not adequately defined and that there are no objective criteria
for establishment of an LOV. These deficiencies could result in
establishment of an LOV based solely on analyses of structure
susceptible to multiple site damage and multiple element damage,
without consideration of more relevant and reliable data, such as test
evidence and service experience. These commenters concluded that, in
these circumstances, airplanes could be operated well past the point to
which the engineering data supports safe operation.
    The commenters recommended that the required evaluation explicitly
include the following tasks, which are described in the AAWG's 2003
report \28\ as necessary to establish or extend an LOV.
---------------------------------------------------------------------------

    \28\ AAWG, Widespread Fatigue Damage Bridge Tasking Report, July
23, 2003.
---------------------------------------------------------------------------

    1. Ensure that the basics of the Aging Aircraft Program are in
existence.
    2. Collect data necessary to extend fatigue test evidence.
    3. Perform analysis of the structure for multiple site damage and
multiple element damage.
    4. Create and update maintenance documents to include maintenance
actions and modifications for those areas where it has been predicted
that multiple site damage and multiple element damage will occur before
the proposed LOV.
    In addition, industry representatives on the AAWG and Boeing
recommended that the rule explicitly use the term ``fatigue test
evidence'' to refer to the collective body of information that should
be considered in establishing an LOV. The FAA agrees that the first
task, having basics of the four elements of the Aging Aircraft Program
in place,\29\ is an important element for continued safe operation out
to LOV. However, as discussed in the NPRM, this final rule does not
include requirements related to those initiatives because they are
already mandated by airworthiness directives, operational rules, and
airworthiness limitations.
---------------------------------------------------------------------------

    \29\ Mandatory modification, corrosion prevention and control,
supplemental structural inspection, and repair assessment.
---------------------------------------------------------------------------

    The FAA considers that tasks 2 and 3 are implicit in the text of
the proposed rule but agrees that proposed Sec.  25.1807 could be
misinterpreted and result in too much reliance on results of analysis
to preclude WFD up to the LOV. This was not our intent. In fact, as
discussed in the NPRM, our intent was consistent with the AAWG's
recommendations regarding WFD.
    In response to these commenters, the FAA has revised the proposed
rule to clarify how the LOV is to be established. This final rule
specifies that--for an LOV to be acceptable--the supporting evaluation
must demonstrate that the fatigue characteristics and any specified
maintenance actions for the airplane are sufficient to prevent WFD from
occurring before the LOV.
    The required demonstration typically involves an evaluation of the
airplane structure to determine its susceptibility to WFD and, if the
structure is susceptible, an evaluation indicating that WFD will not
occur before the proposed LOV. The evaluation must be supported by test
evidence and analysis. The design approval holder may augment the test
evidence and analysis with any available service experience, or service
experience and teardown inspection results of high-time airplanes.
Service experience and teardown inspection results must be of airplanes
of similar structural design and must account for differences in
operating conditions and procedures. After seeing these changes to the
rule as they were described in the Technical Document, Boeing stated
that it supports the FAA's adoption of an airplane-level assessment of
fatigue test evidence as the basis for both the determination and
extension of LOV.
    The FAA is using the term ``test evidence'' to align with the rule
text of Sec.  25.571 relative to WFD. Therefore, in the context of this
final rule, test evidence is data derived from full-scale fatigue
testing, which may be of the complete airplane, or of separate major
sections of the airplane, or a combination of the two. The test
evidence would be used to support the proposed LOV for an airplane
model. The amount of test evidence required to show compliance would
depend on where a design approval holder proposes to set an LOV and
what data (such as test evidence or service experience) already exist.
    For a new airplane model that is pending approval, there should be
test evidence to address all WFD-susceptible structural areas of an
airplane. The test duration should be at least two times the proposed
LOV. The test evidence may be from prior full-scale fatigue tests
performed by the applicant or others on similar structure. For
derivative models, the applicant should compare the derivative model to
the tested model. To use the test evidence from the original
certification project or previous derivatives, the applicant should
show that the derivative model does not significantly change the basic
structural design concept, aerodynamic contour, and internal load
distribution. Advisory Circulars 120-YY and 25.571-1X further describe
considerations for when existing test evidence could be used.
    For some older airplanes, fatigue test data may be limited to
fuselage structure. This is because the pressurized fuselage has been
considered to be the most fatigue-critical part of the airplane. The
wing and empennage have typically been considered less critical and, as
a result, relevant test data may not exist. However, for these same
airplane models, significant service experience does exist. The FAA
would accept a combination of test evidence and analysis as well as
service experience as data to show compliance with this final rule.
    For example, in the case of one of the pre-Amendment 25-45 airplane
models, significant numbers of airplanes both in service and in storage
have accumulated flight cycles in excess of the design service goal.
For this model, there is significant existing test evidence for the
fuselage, but very little for the wing. In this case, the FAA expects
that demonstrating freedom from WFD for the wing would be based
primarily on service experience; for the fuselage, it would be based
primarily on service experience and test evidence. Advisory Circular
120-YY further describes considerations for when service experience
could be used to supplement existing fatigue testing that is limited to
certain major components of the airplane, such as the fuselage.

    The FAA has used the term ``analysis'' to include fatigue and
damage tolerance analyses. Teardown inspections of in-service airplanes
and fatigue test articles should be performed to the degree necessary
to validate that the test evidence, analysis, and service experience
are representative of the fatigue performance of the airplane out to
the LOV. Design approval holders must explain in their certification
plan how they intend to substantiate their proposed LOV. The FAA has
revised AC 120-YY to provide further guidance on the steps to take for
establishing an LOV.
    As discussed in the NPRM, design approval holders are not required
to identify and develop maintenance actions if they can show that such
actions are not necessary to prevent WFD before the airplanes reach
LOV. If they choose to establish LOVs that rely upon maintenance
actions to prevent WFD before the LOV, they must identify those actions
and, unless the necessary service information already exists, develop
the service information in accordance with a binding schedule approved
by the FAA. Those actions would then be mandated, not by today's rule,
but by future airworthiness directives.
    To be approved, the ``binding schedule'' for necessary maintenance
actions must ensure that the service information is provided in a
``timely manner.'' In the NPRM, the FAA explained that the purpose of
this requirement was to enable the FAA to issue the necessary
airworthiness directives in time to allow operators to accomplish these
actions during normal maintenance. The intent is to allow design
approval holders the flexibility to focus their efforts on initially
developing service information on those maintenance actions that must
be accomplished first. At the same time, the FAA expects design
approval holders to devote sufficient resources to these efforts so
that:
     The service information is available when the FAA needs it
to initiate the airworthiness directive rulemaking process, including
providing public notice and opportunity to comment; and
     The resulting airworthiness directives will provide
sufficient compliance times so that the required actions can be
accomplished without disrupting operators' normal maintenance
schedules.
    Airbus stated that the analysis is the driver for substantiating
LOVs and that test evidence supports the analysis.
    Analysis methods are used in combination with the engineering data
to characterize WFD behavior to the degree necessary to determine if
maintenance actions are required prior to the proposed LOV. As a
result, test evidence and analysis are both required to demonstrate
freedom from WFD. This is consistent with the existing requirements of
Sec.  25.571 at Amendment 25-96.
    We agree that a design approval holder may not have both service
experience and teardown inspection results available to use as part of
its compliance data. We have modified the requirement so that a design
approval holder may have either service experience or service
experience and results of teardown inspections. The change is follows:
    ``This demonstration must include an evaluation of airplane
structural configurations and be supported by test evidence and
analysis at a minimum and, if available, service experience, or service
experience and teardown inspection results, of high-time airplanes of
similar structural design, accounting for differences in operating
conditions and procedures.''

I. How To Extend LOVs

    Proposed Sec.  25.1811 provided that any person could apply to
extend an operational limit, using a process similar to that for
establishing the initial operational limit. The configuration to be
evaluated would consist of not only all model variations and
derivatives approved under the type certificate for which the extension
is sought, but also all structural repairs, alterations, and
modifications to those airplanes, whether mandated by airworthiness
directive or not.
    Section 26.23(b) of this final rule (proposed as Sec.  25.1811)
contains requirements for obtaining approval of an extended LOV that
corresponds to the period of time, stated as a number of total
accumulated flight cycles or flight hours or both, beyond an existing
LOV during which it is demonstrated that WFD will not occur in the
airplane. This demonstration must include an evaluation of airplane
structural configurations and be supported by test evidence and
analysis at a minimum and, if available, service experience, or service
experience and teardown inspection results of high-time airplanes of
similar structural design, accounting for differences in operating
conditions and procedures. Requirements for this section are the same
as those for establishing an LOV. The FAA has removed the requirement
to evaluate repairs, alterations, and modifications from Sec.  26.23.
1. Change the Procedure for Extending LOVs
    Industry representatives on the AAWG, ATA, Cessna, Airbus, United
Parcel Service, FedEx, Boeing, and American Airlines stated that the
means proposed in Sec.  25.1811 for extending an operational limit is
administratively difficult, impractical, and technically unachievable.
The commenters expressed doubt that the proposed process could be
realistically or uniformly accomplished because different operators
will be involved in extending the LOV for the same airplane model.
Furthermore, said the commenters, it is unlikely that any single
operator has the information necessary to obtain an extended LOV. The
cost, and uncertainty about the outcome of the evaluation, would make
this process nearly impossible for an operator to attempt.
    The commenters added that extending an LOV would need to be done by
addressing each individual airplane, identified by tail number, whereas
the maintenance actions which support the initial LOV are based on
statistics pertaining to behavior of the entire fleet of a particular
model. Thus, the method of determining maintenance actions to preclude
WFD out to the LOV is not valid for a single airplane. The AAWG
industry representatives recommended that establishing an extended LOV
and evaluating repairs, alterations, and modifications be a sequential
process. The first step would be to establish the extended LOV. The
second step would be for each design approval holder for a modification
to evaluate its own design relative to the extended LOV and obtain a
separate, independent approval for its design. The operator would
continue to be responsible for assembling all maintenance requirements,
depending on actual airplane configuration, and for obtaining approval
of the maintenance program from the principal maintenance inspector.
Such a process is similar to industry proposals for compliance with the
Aging Airplane Safety Final Rule.
    Several commenters also remarked that the administrative process
for obtaining an amended type certificate or supplemental type
certificate will be extraordinarily difficult to manage because
manufacturers, operators, and holders of supplemental type certificates
do not necessarily have access to each other's proprietary information.
The existing business and legal agreements in place did not contemplate
the high degree of data disclosure that will be required to develop WFD
guidance material and

data needed for an amended type certificate or supplemental type
certificate. Furthermore, many transport airplanes are converted to
operate in different roles than those for which they were originally
designed. Often operators cannot obtain support or design data from
design approval holders because the latter have concerns about
liability, are no longer in business, or are more motivated to sell new
airplanes than to support old ones.
    Several commenters recommended that the FAA delete proposed Sec.
25.1811 and revise proposed Sec.  25.1807 to allow extension of an LOV
by a process approved by the Administrator. They base their
recommendation on the fact that the technical requirements for
establishing an LOV are no different from those for establishing an
extended LOV.
    The FAA agrees that, given the extensive information required to
develop guidelines for including a WFD evaluation of repairs,
alterations, and modifications, the proposed requirements for extending
the LOV needed to be changed. As discussed earlier, the FAA has removed
those requirements. As a result, this final rule includes requirements
for extending an LOV based on the original LOV airplane configuration
plus all new structural modifications or replacements mandated by
airworthiness directives. The FAA has revised requirements of Sec.
26.23(b) to be consistent with Sec.  26.21(b). As previously stated, if
our research demonstrates that additional actions are needed to address
risks for repairs, alterations, and modifications, the FAA will
consider further rulemaking.
    The FAA does not agree with the suggestions to allow extension of
an LOV using a process approved by the Administrator. In this final
rule, requirements for extending an LOV are similar to those for
establishing the first LOV. However, the design approval holder is not
required to develop the data to support an extended LOV because such
extensions are optional. The extended LOV and associated maintenance
actions (inspections, modifications, or replacements) must be defined
within the Airworthiness Limitations section for the airplane. This
requirement is unchanged from the proposed requirements of Sec.
25.1811(b) of the NPRM. As stated in the NPRM, the FAA intends to use
airworthiness directives to mandate any maintenance actions necessary
to reach the LOV established under Sec.  26.21, so that operators will
have an opportunity to comment on the proposed maintenance actions. It
is not necessary to use this process for extensions of the LOV,
however, because the extended LOV would include all maintenance actions
at the time of approval. For these reasons, the FAA has kept
requirements for extending an LOV separate from Sec.  26.21. The FAA
has revised AC 120-YY to provide guidance on establishing an extended
LOV.
2. Evaluation of Repairs, Alterations, and Modifications for an LOV
Extension
    EASA stated that certain existing repairs, alterations, and
modifications should be evaluated for WFD when the LOV is being
extended. EASA states that the risk of WFD increases for repairs,
alterations, and modifications as airplanes age.
    As discussed elsewhere in this document, an extension should be
based on the airplane's structural configuration, just as the initial
LOV is. Persons establishing extensions to LOVs may identify conditions
or limitations in the Airworthiness Limitations section of the
Instructions for Continued Airworthiness that apply to the extensions.
For example, the LOV extension may only be valid for airplanes that
operate at a certain cabin differential pressure or maximum takeoff
gross weight. Operators may have to evaluate their airplanes and take
certain actions prior to incorporating any extensions. AC 120-YY
provides additional guidance on this.
3. Alternate Means of Compliance (AMOCs)
    APA commented that operators should not be allowed alternate means
of compliance (AMOCs) for the WFD rule because, it says, if the FAA
allows AMOCs as it does with airworthiness directives, the ability to
collect data and track compliance will be greatly complicated. Each
operator, said the commenter, will comply in a manner with the least
financial impact to its company. This may or may not be supported by
the ongoing efforts of the original equipment manufacturers to develop
analysis techniques and procedures. It will also add significant
financial costs to the original equipment manufacturers and the FAA to
support, track, and verify each AMOC.
    The initial LOV is established and approved under Sec.  26.21 or
Sec.  25.571. Any extension to the initial LOV or any subsequent LOV is
established and approved under Sec.  26.23. The FAA does not issue
AMOCs for these regulations. Any deviation from a rule is handled via
the procedures contained in 14 CFR part 11.
    Under Sec.  26.21, any maintenance actions needed to support the
initial LOV will be mandated by airworthiness directives, and
compliance with those airworthiness directives and the ability to apply
for an AMOC for those maintenance actions will not involve procedures
that are any different from those used for airworthiness directives
today. An AMOC for the maintenance actions for an initial LOV will not
affect the LOV itself.
    Under Sec.  26.23, however, any maintenance actions developed to
support the extended LOV will be incorporated into the Airworthiness
Limitations section of the Instructions for Continued Airworthiness.
The maintenance actions for extended LOVs will not be published in
airworthiness directives.
4. Extension Procedure Doesn't Allow Public Comment
    ATA and Northwest Airlines stated that the proposed rule does not
permit the public to comment on extensions to LOVs and the maintenance
actions that support them. Extensions to LOVs mandated by airworthiness
directive would allow the opportunity for public comments on extended
LOVs.
    Although mandating LOV extensions by airworthiness directive would
allow the public the opportunity to comment, the FAA does not agree
with the suggestions to use airworthiness directives to allow extension
of an LOV. This is for two reasons:
     Approving an extended LOV isn't rulemaking; it's a finding
of compliance with the applicable regulatory standard (i.e., freedom
from WFD).
     If the FAA doesn't extend the LOV, or subsequent
extensions of that LOV, there's no unsafe condition justifying an
airworthiness directive, because affected airplanes are grounded when
they reach the LOV.
    The FAA has revised AC 120-YY to provide guidance on establishing
an extended LOV.
    The AAWG recommended in its Task 3 Report that design approval
holders and operators work together in establishing LOVs and LOV
extensions. Under today's rule, the FAA expects that design approval
holders and operators will work together when persons are seeking
approval for extended LOVs.

J. Applicability for Existing Airplanes

    The rule proposed in the NPRM would apply to existing transport
category airplanes with a maximum takeoff gross weight greater than
75,000 pounds, by virtue of either the original type certification of
the airplane or a later increase, that are operated under part 121 or
129.

    This final rule applies to certain existing transport category,
turbine-powered airplanes with a maximum takeoff gross weight greater
than 75,000 pounds and a type certificate issued after January 1, 1958,
regardless of whether the maximum takeoff gross weight is a result of
an original type certificate or a later design change. In addition, it
applies to transport category, turbine-powered airplanes with a type
certificate issued after January 1, 1958, if a design change approval
for which application is made after the effective date of the rule has
the effect of reducing the maximum takeoff gross weight from greater
than 75,000 pounds to 75,000 pounds or less. It also applies to
operators of those airplanes being operated under part 121 or 129.
1. Type Certificates Issued After January 1, 1958
    As proposed, applicability of the rule was not limited to turbine-
powered airplanes with type certificates issued after January 1, 1958.
Everts Air Cargo requested that McDonnell Douglas Model DC-6 airplanes
be excluded from applicability, and Boeing requested that both the DC-6
and DC-7 be excluded. Everts Air Cargo stated that its airplanes are
non-pressurized, which should reduce the risk that they would develop
WFD. Both Boeing and Everts pointed out that Sec. Sec.  121.370a and
129.16 of the Aging Airplane Safety Final Rule apply only to certain
transport category, turbine-powered airplanes with a type certificate
issued after January 1, 1958. The commenters recommended that the rule
pertaining to WFD apply only to those same airplanes.
    The FAA agrees that certain parts of the applicability of this
final rule should align with the Damage Tolerance Data Rule and the
Aging Airplane Safety Final Rule and other aging airplane rules, such
as EAPAS/FTS. The McDonnell Douglas DC-6 and DC-7 airplanes have not
had a damage tolerance assessment and have not been included in the
Damage Tolerance Data Rule. In addition, the risk from excluding these
airplanes is small because there are so few of them.
    Therefore, in this final rule the FAA has added the phrase
``transport category, turbine-powered airplanes with a type certificate
issued after January 1, 1958'' to the applicability provisions of Sec.
26.21 and to the operating rules. The change means that the following
airplanes, which would have been affected by the proposal, are not
subject to this final rule:
     McDonnell Douglas Models DC-6 and DC-7.
     Lockheed Model 1649A-98.
     Lockheed Model 1049 Series.
     Lockheed Models 49-46, 149-46, 649-79, 649A-79, 749-79,
and 749A-79.
2. Original Type Certification
    The applicability provision in proposed Sec.  25.1807 included
airplanes with maximum takeoff gross weights exceeding 75,000 pounds,
as approved during original type certification, as well as airplanes
with lower weights that had been increased to greater than 75,000
pounds through later design changes. This applicability provision was
intended to address two situations. In the past, some designers and
operators avoided applying requirements mandated only for airplanes
over a specific capacity by receiving a design change approval for a
slightly lower capacity. By referencing the capacity resulting from
original type certification, the NPRM removed this means of avoiding
compliance.
    Similarly, an airplane design could be originally certified with a
capacity lower than the minimum specified in the rule, but through
later design changes, the capacity has been increased above this
minimum. The reference in the NPRM to a later increase in capacity was
intended to ensure that, if this occurs, the design would have to meet
the requirements of the rule.
    The applicability proposed in the NPRM did not distinguish among
design changes based on whether their date of application for design
approval occurred before or after the rule's effective date. That
provision in proposed Sec.  25.1807 is similar to that for the EAPAS/
FTS, Fuel Tank Flammability, and Damage Tolerance Data Rules. In
addition, the reference to capacity resulting from original type
certification is common to proposed Sec.  25.1807 and the other rules.
The agency has determined that the approach to applicability under
today's rule should be slightly different from that used in previous
rules. This is to avoid requiring design approval holders to establish
LOVs for models that have maximum takeoff gross weights that were
decreased to 75,000 pounds or less by an amended type certificate or
supplemental type certificate before the effective date of today's
rule. Applicants for such design changes in the past could not have
designed the airplanes' capacities to avoid complying with today's
requirements, and it is not our intent to include them in the
applicability of this final rule.
    The FAA has revised this section (now Sec.  26.21) to apply to
transport category, turbine-powered airplanes with a maximum takeoff
gross weight greater than 75,000 pounds and a type certificate issued
after January 1, 1958, regardless of whether the maximum takeoff gross
weight is a result of an original type certificate or a later design
change. This section also applies to transport category, turbine-
powered airplanes with a type certificate issued after January 1, 1958,
if a design change approval, for which application is made after the
effective date of the rule, has the effect of reducing the maximum
takeoff gross weight from greater than 75,000 pounds to 75,000 pounds
or less.
    The FAA has also revised the applicability of Sec. Sec.  121.1115
and 129.115 to be consistent with the applicability of Sec.  26.21 for
existing airplanes. For future airplanes for which an LOV is approved
in accordance with Sec.  25.571 of today's rule, we have retained the
requirement that Sec. Sec.  121.1115 and 129.115 apply to operators of
U.S.-registered transport category, turbine-powered airplanes,
regardless of the maximum takeoff gross weight. For future design
changes reducing the maximum takeoff gross weight from greater than
75,000 pounds to 75,000 pounds or less, the compliance date for
operators is 30 months after the effective date of the rule, or the
date of design change approval, or the date specified in the plan
approved under Sec.  25.571(b), whichever occurs latest. For these
design changes, unless or until the design approval holder complies
with Sec.  26.21 by establishing a new LOV, the LOV applying to the
airplane in the absence of the design change would still apply.
3. Airplane Configuration
    This final rule requires that holders of type certificates for
existing airplanes evaluate certain configurations of those airplanes
for susceptibility to WFD and use the results of the evaluation to set
LOVs for those airplanes. The configurations to be evaluated are:
     All model variations and derivatives approved under the
type certificate, and
     All structural modifications and replacements to those
airplanes which were mandated by airworthiness directives issued to
address any configuration developed by the design approval holder.
    In the NPRM, the FAA proposed evaluation of the same airplane
configurations.
    In their comments, the industry representatives on the AAWG,
Boeing, and Airbus expressed concern about the proposed requirement to
evaluate all structural modifications and

replacements mandated by airworthiness directives. Airbus stated that
this approach deviates from all previous industry recommendations and
will lead to a significant increase in configurations to be assessed.
The industry representatives on the AAWG, Boeing, and Airbus requested
that the FAA reconsider this requirement and focus only on
airworthiness directives which have been issued specifically to address
WFD.
    The FAA issues many airworthiness directives which require
structural modifications or replacements not intended to address WFD.
These required modifications or replacements, however, may affect
susceptibility of a structure to WFD. A modification might introduce
new details that cause a structure which was previously not susceptible
to WFD to become susceptible, or make a change that increases
susceptibility so that previously established maintenance actions need
to be modified. Because today's rule is intended to address the
potential for WFD in airplanes as they are actually configured, we must
address these required modifications. It would serve no useful purpose
to evaluate structural configurations which no longer exist in service
because airworthiness directives have required modifications to those
configurations.
    Modifications mandated by airworthiness directives are much fewer
in number than other modifications, and they generally affect airplanes
of the same model in the same way. Many modifications mandated by
airworthiness directives would not affect the potential for WFD; others
could.\30\ Therefore, the FAA is today issuing this requirement as
proposed.
---------------------------------------------------------------------------

    \30\ Advisory Circular 120-YY provides guidance on which
modifications mandated by airworthiness directives should be
assessed by the design approval holder.
---------------------------------------------------------------------------

4. Weight Cutoff
    In the preamble to the proposed rule, the FAA stated that the
agency had considered applying the rule to all existing transport
category airplanes, regardless of the maximum takeoff gross weight. The
FAA acknowledged that using a weight cutoff of greater than 75,000
pounds excludes approximately 1,600 regional jets operating under parts
121 or 129, giving the impression that this rule might not align with
our ``One Level of Safety'' initiative. However, the FAA justifies the
proposed weight cutoff on the basis of the relatively young age of the
regional jet fleet. Because those airplanes are younger, they have a
low present risk for WFD.
    Embraer agreed that existing regional jet airplanes should not be
subject to the rule at this time, stating that the airplanes have
typically been certificated to damage tolerance requirements. Other
commenters--such as the National Transportation Safety Board, Transport
Canada, the Air Line Pilots Association (ALPA), EASA, and an individual
commenter--did not agree, because the regional jets are at risk of
developing WFD as they accumulate flight cycles just as larger
airplanes are. The ALPA recommended that the FAA form a study group to
assess WFD in lighter airplanes. Pending a detailed risk analysis, the
association suggested a weight cutoff of 12,000 pounds.
    The 75,000 pound weight cutoff was based on recommendations from
the AAWG for WFD rulemaking. The overwhelming majority of passengers
and cargo are carried by airplanes with a maximum gross takeoff weight
of greater than 75,000 pounds. Inclusion of airplanes below that limit
and above 12,500 pounds is under study by the FAA and if service
experience shows a need to include those airplanes, rulemaking will be
considered to include them.
    The FAA's highest priority is to address the oldest airplanes at
highest risk of WFD--namely, airplanes with a maximum takeoff gross
weight greater than 75,000 pounds. However, the FAA recognizes that the
lighter and relatively younger regional jets will also be at risk of
developing WFD as they accumulate flight cycles. We will reassess the
fleet, including those airplanes below 75,000 pounds, after this rule
has been implemented, to determine whether further rulemaking is
necessary.
5. Default LOVs and Excluded Airplanes
a. Table 1--Default LOVs
    In the proposed operational requirements in the NPRM, the FAA
inadvertently created an ambiguity regarding the obligations of
operators of airplanes for which the design approval holder might fail
to establish an LOV as required. While the FAA fully anticipates that
affected design approval holders will comply with the requirements of
this final rule, there is a need to clearly provide for what happens if
one or more does not. As proposed, paragraph (a) of Sec. Sec.  121.1115
and 129.115 would apply to operators of airplanes for which an LOV
``has been established.'' Paragraph (b) of these sections requires that
operators incorporate approved LOVs.
    Our expectation was that, if a design approval holder failed to
comply with the requirement to obtain approval for an LOV, the operator
or operators, in order to continue to operate the affected airplanes,
would themselves obtain the necessary approval. Because they would not
have access to the design approval holder's data necessary to perform a
WFD evaluation, they would likely have to rely on the design service
goals and extended service goals set forth in Table 3 of the NPRM (see
below). As stated in the NPRM, ``After June 18, 2008, an affected
operator could not operate an airplane unless the operator has
incorporated an Airworthiness Limitations section approved under
Appendix H to part 25 or Sec.  25.1807 into its maintenance program.''
    The FAA now recognizes that the final rule should explicitly define
operators' obligations if the design approval holder fails to comply.
Therefore, the FAA has revised the operational rules to state that, in
the absence of an approved LOV, the operator must incorporate the
applicable LOV specified in Table 1 \31\ of either Sec.  121.1115 or
Sec.  129.115. The table also adds flight hour numbers for design
service goals for airplanes for which that information was available.
---------------------------------------------------------------------------

    \31\ To develop Table 1, the FAA added airplanes to Table 3,
deleted airplanes from Table 3, and split Boeing Models 737, 747,
and 777 airplanes into two groups. These airplanes were added:
Airbus A318 and A380; Bombardier CL-600 (2D15 and 2D24); and Embraer
ERJ-170 and ERJ-190. The following airplane models were deleted:
Boeing 707 and 720; Bombardier CL-44 and BD-700; British Aerospace
Airbus, Ltd. BAC 1-11; British Aerospace (Commercial Aircraft) Ltd.
Armstrong Whitworth Argosy A.W. 650 Series 101; BAE Systems
(Operations) Ltd BAe 146A (all models), Avro 146 RJ70A, Avro RJ85A,
and Avro RJ100A.
---------------------------------------------------------------------------

    The inclusion of default LOVs in Table 1 does not prevent an
operator from developing its own LOV under Sec.  26.23 of this final
rule. The rule specifies that--
     The design approval holder must establish an LOV, and
     If an LOV is not approved, an operator must use the
default LOV in Table 1. If an operator later chooses to establish an
LOV under Sec.  26.23, that LOV will be considered an extended LOV.
    This provision eliminates any need for operators to obtain a
separate approval for these ``default'' LOVs. It also eliminates the
risk that a relatively young airplane would be grounded as of an
operator's compliance date simply because the FAA had not approved an
LOV for that airplane.
    Boeing stated that the default LOVs published in the Technical
Document are without context and could be misused. Boeing said that it
could provide more appropriate numbers to

use, but that these numbers should be removed from the rule because
Boeing intends to comply with the rule.
    The default LOVs in Table 2 of Sec.  121.1115 and Sec.  129.115 are
intended to be used by persons who may choose to operate one of the
excluded airplanes. They may also be used by other operators if a
design approval holder is late in establishing an LOV, in order to
prevent airplanes with fewer accumulated flight cycles and flight hours
than the default LOV from being grounded. A few airplanes, such as the
Airbus A380, already have an operational limitation included in their
Airworthiness Limitations section. These are referenced in the table by
a NOTE, and may be used as a default LOV.

           Figure 3--Comparison of NPRM Design and Extended Service Goals and Final Rule Default LOVs
----------------------------------------------------------------------------------------------------------------
                                                 NPRM table 3             Final rule Sec.  Sec.   121.1115 and
                                        ------------------------------              129.115 table 1
             Airplane model                                           ------------------------------------------
                                          Design and Extended Service     Default LOVs [flight cycles (FC) or
                                             Goals (flight cycles)                 flight hours (FH)]
----------------------------------------------------------------------------------------------------------------
Airbus:
    A300 B2 Series \32\................  48,000......................  48,000 FC
    A300 B4-100 Series \33\............  40,000......................  40,000 FC
    A300 B4-203........................  34,000......................  34,000 FC
    A300-600 Series \34\...............  30,000......................  30,000 FC/67,500 FH
    A310-200 Series (all models).......  40,000......................  40,000 FC/60,000 FH
    A310-300 Series (all models).......  35,000......................  35,000 FC/60,000 FH
    A318 Series (all models)...........  None provided...............  48,000 FC/60,000 FH
    A319 Series (all models)...........  48,000......................  48,000 FC/60,000 FH
    A320-100 Series (all models) \35\..  48,000......................  48,000 FC/48,000 FH
    A320-200 Series (all models) \35\..  48,000......................  48,000 FC/60,000 FH
    A321 Series (all models)...........  48,000......................  48,000 FC/60,000 FH
    A330-200, -300 Series (except WV050  40,000......................  40,000 FC/60,000 FH
     family) (non enhanced) \36\.
    A330-200, -300 Series WV050 family   40,000......................  33,000 FC/100,000 FH
     (enhanced) \36\.
    A330-200 Freighter Series..........  None provided...............  NOTE \38\
    A340-200, 300 Series(except WV 027   20,000......................  20,000 FC/80,000 FH
     and WV050 family) (non enhanced)
     \37\.
    A340-200, 300 Series WV 027 (non     20,000......................  30,000 FC/60,000 FH
     enhanced) \37\.
    A340-300 SeriesWV050 family          20,000......................  20,000 FC/100,000 FH
     (enhanced) \37\.
    A340-500, 600 Series (all models)    20,000......................  16,600 FC/100,000 FH
     \37\.
    A380-800 Series (all models).......  None provided...............  NOTE \39\
Boeing:
    Boeing 707 (-100 Series and -200     20,000......................  Excluded per Sec.   26.21(g)
     Series).
    Boeing 707 (-300 Series and -400     20,000......................  Excluded per Sec.   26.21(g)
     Series).
    717 (all models)...................  60,000......................  60,000 FC/60,000 FH
    Boeing 720.........................  30,000......................  Excluded per Sec.   26.21(g)
    727 (all models)...................  60,000......................  60,000 FC
    737 (Classics): 737-100, -200, -     75,000......................  75,000 FC
     200C, -300, -400, -500 \40\.
    737 (NG): 737-600, -700, -700C,      75,000......................  75,000 FC
     800, 900 \40\.
    737-900ER..........................  None provided...............  75,000 FC
    747 (Classics): 747-100, -100B, -    20,000......................  20,000 FC
     100B SUD, -200B, -200C, -200F, -
     300, -747SP, 747SR \41\.
    747-400: 747-400, -400D, -400F \41\  20,000......................  20,000 FC
    757 (all models)...................  50,000......................  50,000 FC
    767 (all models)...................  50,000......................  50,000 FC
    777-200, -300 \42\.................  44,000......................  40,000 FC
    777-200LR, 777-300ER \42\..........  44,000......................  40,000 FC
    777F...............................  None provided...............  11,000 FC
Bombardier:
    CL-44D4 and CL-44J.................  20,000......................  Excluded per Sec.   26.21(g)
    CL-600: 2D15 (Regional Jet Series    None provided...............  60,000 FC
     705), 2D24 (Regional Jet Series
     900).
British Aerospace Airbus, Ltd.:
    BAC 1-11 (all models)..............  85,000......................  Excluded per Sec.   26.21(g)
British Aerospace (Commercial Aircraft)
 Ltd.:
    Armstrong Whitworth Argosy A.W. 650  20,000......................  Excluded per Sec.   26.21(g)
     Series 101.
BAE Systems (Operations) Ltd.:
    BAE 46 (all models) and Avro 146     50,000......................  Excluded per Sec.   26.21(g)
     RJ70A, RJ85A and RJ100A (all
     models).
Embraer:
    ERJ 170 (all models)...............  None provided...............  NOTE \43\
    ERJ 190 (all models)...............  None provided...............  NOTE \44\
Fokker:
    F.28 Mark 70, Mark 100 (all models)  90,000......................  90,000 FC
Lockheed:
    300-50A01 (USAF C 141A)............  20,000......................  Excluded per Sec.   26.21(g)
    L-1011 (all models)................  36,000......................  36,000 FC
    188 (all models)...................  26,600......................  26,600 FC

    382 (all models)...................  20,000......................  20,000 FC/50,000 FH
    1649A-98...........................  20,000......................  Excluded per Sec.   26.21(a)
    1049-54, 1049B-55, 1049C-55, 1049D-  20,000......................  Excluded per Sec.   26.21(a)
     55, 1049E-55, 1049F-55, 1049G-8249-
     46, 149-46, 649-79, 649A-79.
    749-79, 749A-79....................  20,000......................  Excluded per Sec.   26.21(a)
McDonnell Douglas:
    DC-6 \45\..........................  20,000......................  Excluded per Sec.   26.21(a)
    DC-6A (all models) \45\............  20,000......................  Excluded per Sec.   26.21(a)
    DC-6B (all models) \45\............  20,000......................  Excluded per Sec.   26.21(a)
    DC-7 (all models) \45\.............  20,000......................  Excluded per Sec.   26.21(a)
    DC-8, -8F (all models).............  50,000......................  50,000 FC/50,000 FH
    DC-9 (all models)..................  100,000.....................  100,000 FC/100,000 FH
    MD-80 (all models).................  50,000......................  50,000 FC/50,000 FH
    MD-90 (all models) \46\............  60,000......................  60,000 FC/90,000 FH
    DC-10-10, -15 (all models).........  42,000......................  42,000 FC/60,000 FH
    DC-10-30, -40, -10F, -30F, -40F      30,000......................  30,000 FC/60,000 FH
     (all models).
    MD-10-10F (all models).............  42,000......................  42,000 FC/60,000FH
    MD-10-30F (all models).............  30,000......................  30,000 FC/60,000 FH
    MD-11, -11F (all models)...........  20,000......................  20,000 FC/60,000 FH
Airplanes with Maximum Takeoff Gross
 Weight Changes:
    All airplanes whose maximum takeoff  Design service goals and      There are no default LOVs for airplanes
     gross weight has been decreased to   extended service goals for    whose weight has been changed.
     75,000 pounds or below after         airplanes whose weight has
     January 14, 2011 or increased to     been changed are unknown.
     greater than 75,000 pounds at any
     time by an amended type
     certificate or supplemental type
     certificate.
----------------------------------------------------------------------------------------------------------------
\32\ Listed as A300 B2-1A, B2-1C and B2K-3C in the NPRM.
\33\ Listed as A300 B4-2C and B4-103 in the NPRM.
\34\ Listed as A300 B4-600 Series, B4-600R Series, and F4-600R Series in the NPRM.
\35\ Listed as A320 (all models) in the NPRM.
\36\ Listed as A330 (all models) in the NPRM.
\37\ Listed as A340 (all models) in the NPRM.
\38\ Airplane operation limitation is stated in the Airworthiness Limitation section.
\39\ Airplane operation limitation is stated in the Airworthiness Limitation section.
\40\ Listed as Boeing 737 in the NPRM.
\41\ Listed as Boeing 747 in the NPRM.
\42\ Listed as Boeing 777 in the NPRM.
\43\ Airplane operation limitation is stated in the Airworthiness Limitation section.
\44\ Airplane operation limitation is stated in the Airworthiness Limitation section.
\45\ Airplane certificated before 1958.
\46\ Listed as MD-90-30 in the NPRM.

b. Table 2--Airplanes excluded from Sec.  26.21
    Section 26.21 specifically excludes models of airplanes from
today's rule if no airplanes of that model are operating under part 121
or 129. Today's revisions to parts 121 and 129 requiring that operators
incorporate LOVs into their structural maintenance programs include
applicability to operators of airplanes that have been excluded under
Sec.  26.21 should the operator later decide to operate one of them.
    In the NPRM, the FAA proposed excluding airplanes not operated
under part 121 or 129. The agency proposed exclusion from the rule for:
     Bombardier BD-700.
     Gulfstream GV.
     Gulfstream GV-SP.
     British Aerospace, Aircraft Group, and Societe Nationale
Industrielle Aerospatiale Concorde Type 1.
    The FAA requested comments on the feasibility and benefits of
including or excluding these airplanes. The agency also requested
comments on the feasibility of including or excluding any other
transport category airplanes with a maximum takeoff gross weight
greater than 75,000 pounds from the requirements of this provision,
whether or not they are operated under part 121 or 129.
    Several commenters disagreed with the applicability of the rule, as
proposed. The National Transportation Safety Board recommended that the
final rule also apply to airplanes operated under part 135 because they
may be at equal or greater risk of developing WFD compared to those
operated under parts 121 or 129.
    An individual commenter suggested that the FAA delete the list of
airplanes proposed for exclusion because it gives preferential
treatment to certain airplanes. This commenter added that an operator
had planned to use Gulfstream GV airplanes for part 121 operations but
chose not to do so only for financial reasons. If an operator did
decide to operate an excluded airplane under part 121 or 129, said the
commenter, there would be no operational limit and no associated
maintenance actions to preclude WFD in that airplane. Although this
commenter did not support having a list of excluded airplanes in the
rule, he suggested--based on the agency's stated rationale in the
NPRM--that we add the following airplanes to the list:
     The Douglas DC-6, DC-6A, and DC-7.
     The Lockheed 049, 149, 649, 749, 1049, 1649, 188, 300, and
382.
     The Boeing 707 and 720.

    We have reconsidered our rationale for the list of excluded
airplanes proposed in the NPRM. Those airplanes have a maximum takeoff
gross weight greater than 75,000 pounds but are not currently operating
under part 121 or 129. Therefore, there is no reason to require the
design approval holders to establish LOVs for them. We have decided to
retain on the list the models originally proposed for exclusion from
the rule and, in response to comments, and to be consistent with other
aging airplane rules, have added other models which are not operated
under part 121 or 129. The complete list is shown below.
    (1) Bombardier BD-700.
    (2) Bombardier CL-44.
    (3) Gulfstream GV.
    (4) Gulfstream GV-SP.
    (5) British Aerospace, Aircraft Group, and Societe Nationale
Industrielle Aerospatiale Concorde Type 1.
    (6) British Aerospace (Commercial Aircraft) Ltd., Armstrong
Whitworth Argosy A.W. 650 Series 101.
    (7) British Aerospace Airbus, Ltd., BAC 1-11.
    (8) BAE Systems (Operations) Ltd., BAe 146.
    (9) BAE Systems (Operations) Ltd., Avro 146.
    (10) Lockheed 300-50A01 (USAF C141A).
    (11) Boeing 707.
    (12) Boeing 720.
    (13) deHavilland D.H. 106 Comet 4C.
    (14) Ilyushin Aviation IL-96T.
    (15) Bristol Aircraft Britannia 305.
    (16) Avions Marcel Dassault-Breguet Aviation Mercure 100C.
    (17) Airbus Caravelle.
    (18) D & R Nevada, LLC, Convair Model 22.
    (19) D & R Nevada, LLC, Convair Model 23M.
    The FAA recognizes that it is possible--as suggested by the
individual commenter--that in the future an operator could decide to
operate an ``excluded'' airplane under part 121 or 129. Therefore, in
this final rule Sec. Sec.  121.1115 and 129.115 are revised to provide
that no airplane listed in Sec.  26.21 can be operated under part 121
or 129 unless an LOV for the airplane has been incorporated into the
operator's structural maintenance program. The operational rules state
that, in the absence of an approved LOV, the operator must incorporate
the applicable default LOV specified in Table 2 of either Sec. Sec.
121.1115 or 129.115. Those default LOVs are based on Table 3 of the
NPRM. As stated in the NPRM, Table 3 used design service goals and
extended service goals that were based on information from design
approval holders or on a conservative estimate by the FAA. It did not
include the Comet 4C, IL-96T, Britannia 305, Mercure 100C, Caravelle,
Convair Model 22, or Convair Model 23M. To develop those default LOVs,
the FAA treated flight-cycle or flight-hour data that was available for
those airplanes as fatigue test data and reduced it by a factor of two.
This approach is based in part on AC 25.571-1X for new airplanes.
6. Bombardier Airplanes
    Bombardier asked for clarification of the applicability of the
proposed rule to several of its models and their derivatives.
Specifically, the company asked about the following airplanes:
    Models CL 600 Challenger 870 and 890: Bombardier asked whether they
should be added to the list of excluded airplanes in proposed Sec.
25.1807(i).
    The CL 600 Challenger 870 and 890 do not currently have type
certificates issued by the U.S. Therefore, there are no N-registered
airplanes operating under either part 121 or 129. As a result, this
final rule does not apply to them at this time. However, if Bombardier
were to apply for a U.S. type certificate before the effective date of
this final rule, the company would have to comply by the compliance
date in Sec.  26.21. Even if Bombardier were to apply after the
effective date of the rule, the company would be subject to
requirements of Sec.  26.21 because the Bilateral Aviation Safety
Agreements (BASA) \47\ with Canada allow the U.S. to impose additional
requirements in the interest of safety. Other airplanes in similar
circumstances would be handled in the same way.
---------------------------------------------------------------------------

    \47\ Agreement between the Government of the United States of
America and the Government of Canada for Promotion of Aviation
Safety, June 12, 2000.
---------------------------------------------------------------------------

    Model CL 600 derivatives--RJ 701 ER, RJ 701 LR, all RJ 705
airplanes, and all RJ 900 airplanes: Bombardier noted that Table 3 in
the NPRM, titled Design and Extended Service Goals, does not list these
models.
    The CL 600 derivatives RJ 705 and RJ 900 were inadvertently left
off Table 3 of the NPRM. This final rule applies to Bombardier models
RJ 705 series and RJ 900 series because their maximum takeoff gross
weight is greater than 75,000 pounds, and they are operated under part
121 or 129. They have been added to Table 1, which is the applicability
table for this final rule. Today's rule does not apply to Bombardier RJ
701 series airplanes because their maximum takeoff gross weight is not
greater than 75,000 pounds.
    Model CL 44: These airplanes were previously exempted from the
other aging airplane rules, both proposed and final, on the basis of
their age and the very small number remaining in service.
    Bombardier Model CL 44 is not operated under either part 121 or 129
and, therefore, the FAA has revised the list of excluded airplanes in
Sec.  26.21 of today's rule to include Bombardier Model CL 44.
7. Intrastate Operations in Alaska
    Lynden Air Cargo requested that the NPRM pertaining to WFD be
withdrawn in its entirety. Alternatively, the commenter requested that
Lockheed Model 382 airplanes be excluded from the rule and that all air
carriers engaged in intrastate operations in Alaska be excluded. In
support of this request, the commenter gave the following reasons:
     There is no replacement airplane with the necessary lift
and operational characteristics.
     The L-382 airplanes are not used to carry passengers.
     It is in the public interest to maintain the unique
capabilities of the L-382 in Alaska where it supports remote
communities and projects with no roads or waterways and supports the
U.S. military during critical campaigns and the ongoing war on
terrorism.
    Lynden Air Cargo also asked that it be excluded from Sec.  121.909.
    Senator Murkowski of Alaska and the late Senator Stevens stated
that the rule, as proposed, would have severe consequences to residents
and cargo carriers operating in that State. Senator Stevens referred to
Section 1205 of the Federal Aviation Reauthorization Act of 1996 (49
U.S.C. 40113(f)), which requires that--when modifying regulations
affecting intrastate aviation in Alaska--the FAA consider the extent to
which Alaska is not served by transportation modes other than aviation.
Accordingly, Senator Stevens requested that the FAA exempt all
intrastate operations in Alaska and the interstate operations of the
six Lockheed L-382G airplanes operated by Lynden Air Cargo. The senator
pointed out that the L-382G is out of production and there is no
suitable replacement available.
    Several other commenters addressed operational limits for Lockheed
Models L-382E and G, although they did not discuss operation of these
airplanes in Alaska. Specifically, Transafrik International asked that
Lockheed Models L-382E and G be removed from Table 3 or that their
operational limit be increased to at least 60,000 cycles. The commenter
added that the airplanes are no longer in production and there is no

replacement airplane able to take off and land on short, unimproved
runways with the payloads required. A comment from Lockheed Martin
estimated--based on certain inspections and modifications which it had
performed on the outer and center wing structure--that the LOV for the
Lockheed Model L-382 is 50,000 flight hours but would no doubt be
changed to at least 75,000 flight hours, to accommodate usage in the
fleet. Lockheed Martin also identified maintenance actions that should
be performed on the wing structure to operate to that limit. The
commenter stated that, regardless of any FAA decision on implementation
of the rule, the company will continue to ensure that operators of
Lockheed Model L-382 model aircraft are provided with inspection
procedures and replacement actions that effectively mitigate the risk
of failure due to WFD.
    Consistent with 49 U.S.C. 40113(f), the FAA has carefully
considered the potential impact of this rulemaking on Alaska intrastate
operators to determine whether intrastate service in Alaska would be
adversely affected. Airplanes to which this final rule is applicable
are not operated solely in intrastate commerce in Alaska. Therefore,
contrary to the commenters' assertions, the FAA has determined that
there would not be an adverse effect on intrastate air transportation
in Alaska and that regulatory distinctions are not appropriate.
    The Lockheed L-382G operated by Lynden Air Cargo is operated under
14 CFR part 121, Operating Requirements: Domestic, Flag, and
Supplemental Operations and operates interstate as well as to foreign
destinations. The FAA has decided against excluding the L-382G from
requirements of Sec. Sec.  121.1115 and 129.115 for those airplanes in
interstate operation. The safety rationale for these rules applies
equally to that airplane. In accordance with 14 CFR part 11, Lynden Air
Cargo may submit a petition for exemption from those rules. Such a
petition must state (1) why granting such an exemption would be in the
public interest and (2) why a grant of exemption would not adversely
affect safety or how it would provide a level of safety equivalent to
the regulation.
    Regarding Lynden Air Cargo's request for exclusion from Sec.
121.909, that requirement, which was formerly designated as Sec.
121.370(a), has been in effect since November 1, 2002.\48\ The FAA has
not made any changes to that rule other than changing its section
number.
---------------------------------------------------------------------------

    \48\ 67 FR 72726, December 6, 2002.
---------------------------------------------------------------------------

    The FAA encourages Transafrik and Lynden Air Cargo as well as other
operators of Model L-382G to work with Lockheed Martin regarding the
establishment of the LOV for the model.
8. Composite Structures
    The Modification and Replacement Parts Association (MARPA) and
Airbus asked that the FAA clarify applicability of the rule to
structure made of composite materials, and MARPA recommended that
composite structure should be treated the same as metallic structure.
    There is an increasing trend for manufacturers to use composite
materials to build airplanes. This structure wears differently than
metallic structure. For example with metallic structure, repeated loads
or environmental exposure cause fatigue cracking or corrosion. With
composite structure, repeated loads or environmental exposure cause
general degradation (such as cracking, delamination, and oxidative
breakdown of the resin) and accumulation of local damage (such as
wearing out of fastener holes and handling damage, or water ingression
between composite layers, followed by freeze-thaw cracking of the
core).
    The FAA issued AC 20-107B to provide guidance for certifying
composite structures, including guidance for evaluating composite
structure relative to the damage tolerance requirements of Sec.
25.571.
    The objective of this final rule is to address the normal fatigue
wear out of metallic structure. Although the trend in industry is to
use composite structure as much as possible, a significant percentage
of a new airplane may still be built of metal. Full-scale fatigue test
evidence would be necessary to demonstrate that WFD will not occur in
metallic structure of the airplane. It would also be necessary for the
design approval holder for the airplane to develop an LOV to limit the
operation to the point in time up to which it has been demonstrated
that WFD will not occur in the airplane's metallic structure.
    The FAA will continue to evaluate whether rulemaking is necessary
to address the normal wear of composite structures.

K. Harmonization

    A number of commenters, including industry representatives on the
AAWG, FedEx, Boeing, Embraer, the National Air Cargo Association
(NACA), AWAS, and Airbus noted that the WFD NPRM has not been
harmonized with the European Aviation Safety Agency (EASA), which has
issued Notice of Proposed Amendment (NPA) 05-2006 on this subject, and
other national aviation authorities. The commenters pointed out that
the Initial Regulatory Evaluation did not consider the cost of failing
to harmonize the rule with other airworthiness authorities. Airbus also
questioned whether the evaluation addressed costs associated with
importing into the United States airplanes that have not complied with
the rule, especially if the rule is not harmonized with other
airworthiness authorities.
    They recommended that the FAA harmonize the rule with those
authorities before issuing it. According to the commenters, lack of
harmonization could cause the following problems:
    1. It could create a significant challenge to future certification
projects, encouraging unilateral and possibly arbitrary certification
activities.
    2. There could be a substantial negative economic impact with
respect to the transfer, lease, or sale of aircraft between the U.S.
and other countries. Commenters suggested that bilateral agreements be
amended to support the transfer of used aircraft subject to the final
rule.
    3. The FAA and EASA could have different approaches to WFD.
    4. Type certificate holders from other countries may not be given
the same priority and allocation of FAA resources as are type
certificate holders from this country, resulting in delayed approval
for applications from other countries.
    Boeing, EASA, and Airbus requested that the FAA include the
requirement to evaluate certain repairs, alterations, and modifications
to align its requirements with those being proposed by EASA.
    The FAA is working closely with EASA and other national
airworthiness authorities to harmonize this final rule as much as
possible. On April 25, 2006, EASA published NPA 05-2006, entitled
Ageing Aeroplane Structures. That notice proposed technical guidance to
be used for developing programs for continuing structural integrity, to
ensure that the structure of aging airplanes is adequately maintained
throughout their operational lives. Among other things, the notice
proposed guidance for addressing WFD in existing airplane models. The
FAA has provided comments on that proposed rulemaking. EASA is
considering our comments and has discussed them with us.
    Many of the changes made to our proposed rule will facilitate
harmonization with national airworthiness authorities. Some of these
changes are the following:

    1. The design approval holder requirements proposed in the NPRM as
part 25, subpart I, are now contained in a new part 26 to harmonize
more easily with the regulatory structure of other national
airworthiness authorities.
    2. This final rule uses the term ``limit of validity'' rather than
``initial operational limit'' to align more closely with other national
airworthiness authorities.
    3. This final rule uses compliance dates that specify a phased
approach for establishing the LOV for existing airplane models. NPA 05-
2006 links compliance dates to design service goals. As discussed
above, the FAA has concluded that the latter approach creates
unnecessary complexity and uncertainty. We have submitted comments
about this matter to EASA and are in discussions about it. In terms of
establishing an LOV, the technical guidance in AC 120-YY is consistent
with EASA's technical guidance in NPA 05-2006.
    4. With respect to removal of requirements pertaining to repairs,
alterations, and modifications, the FAA is working closely to harmonize
this final rule with the rule EASA is developing but has not yet
published for public comment.
    5. Finally, the changes to Sec.  25.571 are based on a
recommendation of the General Structures Harmonization Working Group of
ARAC. Development of the October 2003 recommendation pertaining to WFD
involved harmonization between U.S. and European requirements.

L. The Regulatory Evaluation for the NPRM

    The estimated present value cost of this final rule is about $3.6
million, while the estimated present value cost of the NPRM was
estimated to be about $360 million. The estimated benefits of this
final rule are worth $4.8 million in present value and are based on
managing WFD with maintenance actions developed under this final rule
versus the current practice of issuing airworthiness directives as WFD
is found. The estimated present value benefits of the NPRM consisted of
$726 million of accident prevention benefits and $83 million of
detection benefits for total benefits of $809 million.
    We received many comments regarding the validity of the regulatory
evaluation of the proposed rule on WFD. In general, commenters stated
that the potential benefits of the rule seemed to be overstated, and
the potential costs seemed to be understated. Therefore, commenters
challenged the conclusion that the benefits of the rule justify the
costs. The commenters included Lockheed Martin, Boeing, Airbus,
Bombardier, NACA, the CAA, ATA, FedEx, United Parcel Service, AWAS,
American Airlines, Lynden Air Cargo, industry representatives on the
AAWG, and an individual commenter.
1. Benefits of Proposed Rule
    Some commenters questioned how a benefit of $726 million could be
attributable to accident prevention when there have been no accidents
related to WFD since the Aloha Airlines accident in 1988. The NACA and
other commenters also argued that the regulatory evaluation makes a
false assumption when it defines the cost benefit number for avoiding
fleet grounding. Finally, the ATA and several other commenters
suggested that projected benefits would decrease if the regulatory
evaluation were updated to include data from the years 1974 through
1983 and 2000 through 2005.
    Today's rule establishes a consistent approach to management of
aging airplanes so that they are not operated to the point where WFD
occurs. Thus the potential benefit of the rule is preventing
catastrophic structural failure in flight that could result in loss of
lives and loss of the airplane. Other benefits of the rule are costs
avoided under the current system. Relying on the issuance of
airworthiness directives to address WFD--whenever it happens to be
discovered--causes unscheduled down time. The issuance of emergency
airworthiness directives and immediately adopted rules may result in
the unscheduled removal from service of a fleet of airplanes.
    This final rule requires a design approval holder to establish an
LOV for an airplane that reflects the fatigue characteristics of the
airplane structure. If the WFD evaluation determines that maintenance
actions are necessary to reach this LOV, the FAA would adopt them
through the normal airworthiness directive process, allowing
opportunity for notice and comment and accomplishment of required
actions during scheduled maintenance. As such, the costs of these
maintenance actions would be lower than if the FAA adopted emergency
airworthiness directives or immediately adopted rules mandating the
same actions as a result of in-service occurrences of WFD. As discussed
below, the FAA expects very few airplanes to be retired solely because
they reach their LOV. We have also taken this into account.
    Our revised regulatory evaluation lists three benefits of the rule,
namely
    (1) Prevention of accidents;
    (2) Extension of the economic life of the airplane with
corresponding revenues from that additional economic life; and
    (3) Near elimination of emergency airworthiness directives
pertaining to WFD, which significantly reduces downtime associated with
urgent unscheduled maintenance. The quantified benefit of the final
rule is based solely on this third benefit, which is valued at $9.8
million or, evenly distributed over 20 years, a present value of
approximately $4.8 million.
2. Costs of Proposed Rule
a. Need To Know LOVs To Determine Cost
    Some commenters stated that, if the operational limit for each
airplane model were not known, then the cost of the rule could not be
determined.
    In our Initial Regulatory Evaluation, the agency estimated the
costs of initial operational limits to operators by using the design
service goal for each airplane model as the initial operational limit.
Those cost estimates would be expected to be higher than estimates
based on LOVs that design approval holders anticipate establishing
because in most cases, these LOVs are expected to exceed the design
service goals. During the comment period, manufacturers provided the
LOVs that they anticipate they will be establishing under today's rule.
Those LOVs were 33% to 180% higher than the airplane's design service
goal. Accordingly, our analysis in the Final Regulatory Evaluation uses
these anticipated LOVs and indicates a lower cost to operators than was
initially projected.
    Airbus stated that not all of its models will have LOVs from 33% to
180% beyond the airplane's design service goal. Airbus will have LOVs
for some models that will be equal to the airplane's design service
goal. Although some of Airbus's LOVs are equal to the design service
goal, which makes the LOVs span a shorter time, we still do not
anticipate that any Airbus airplanes will need to be retired during the
20-year analysis period as a result of this final rule.
    FedEx, Northwest Airlines, and ATA argued that operator cost
estimates are not credible if they are based on anticipated LOVs
instead of LOVs that have been accepted by the FAA and industry. It is
for this reason that FedEx further argued that an operational rule must
be proposed after the design approval holder's LOVs have been approved
by the FAA. This would also, noted the commenter, provide the

public with the opportunity to comment on those LOVs.
    The FAA measures the economic loss to operators of retiring an
airplane at LOV instead of at a planned future retirement date. The FAA
considers that this is a reasonable way to estimate compliance costs
and that, ultimately, the LOVs that are accepted by the FAA and
industry will be very close to those anticipated LOVs that the FAA has
received from industry and used for these estimates of cost.
b. Need To Know Maintenance Actions To Determine Cost
    Some commenters suggested that the costs associated with
maintenance actions to preclude WFD prior to reaching the LOV either
could not be determined or were substantially underestimated because
the actions were not yet developed. Other commenters indicated that
costs used in the regulatory evaluation do not accurately reflect
operators' costs. They said, for example, that estimates of the number
of hours needed to accomplish inspections, the number of inspections
needed in a maintenance visit, and the number of days an airplane is
out of service to accomplish maintenance did not reflect the actual
experience of operators. Boeing added that the overall cost of the rule
is difficult to determine because there will be costs related to
maintenance actions required by airworthiness directives.
    Although this final rule allows design approval holders to
establish LOVs without relying on maintenance actions, the FAA expects
most design approval holders will adopt LOVs that rely on such actions.
As discussed in the NPRM, design approval holders are not required to
identify and develop maintenance actions if they can show that such
actions are not necessary to prevent WFD before the airplanes reach the
LOV. As discussed in the Final Regulatory Evaluation, the FAA
anticipates that at least Boeing will propose LOVs that will depend
upon accomplishment of future maintenance actions. This is consistent
with Boeing's current practice of developing service information that
defines the maintenance actions to address WFD in its products.
However, any maintenance actions necessary to reach the LOV will be
mandated by airworthiness directives through separate rulemaking
actions, so their costs are not attributable to this final rule. This
is also consistent with the current practice of issuing airworthiness
directives to address unsafe conditions associated with WFD. The FAA
will provide cost estimates when issuing the airworthiness directives
for any maintenance actions necessary to prevent WFD.
    The FAA recognizes that this final rule is unusual in that it may
depend upon future rulemaking to fully achieve its safety objectives.
In the context of WFD, this approach is necessary to enable design
approval holders to propose LOVs that allow operators the longest
operational lives for their airplanes, while still ensuring freedom
from WFD. This approach allows for an implementation strategy that
provides flexibility to design approval holders in determining the
timing of service information development (with FAA approval), while
providing operators with certainty regarding the LOV applicable to
their airplanes. The FAA has issued many airworthiness directives in
the past to address WFD issues, and the agency anticipates that the
approach adopted today will interface smoothly with existing practices
for issuing airworthiness directives.
    In this regard, this final rule is similar to SFAR 88, which also
required design approval holders to perform technical evaluations (in
that case, of fuel tank ignition sources) and to develop necessary
maintenance actions that would be mandated by airworthiness directive.
To date, the FAA has issued over 100 airworthiness directives to
address unsafe conditions identified as a result of SFAR 88. These
airworthiness directives were issued based on this proactive approach
of requiring analyses to identify unsafe conditions, rather than
relying on service experience to identify them, with potentially
catastrophic results. In the context of SFAR 88, this approach has been
generally recognized as being effective. The objective of this final
rule is to establish a similar proactive approach that will enable us
to issue any necessary airworthiness directives before WFD results in
potentially catastrophic structural failure.
c. Costs to Manufacturers
    Airbus indicated that, considering the significant number of hours
necessary to train enough engineers and then to comply with the rule,
the Initial Regulatory Evaluation substantially underestimated the
costs of this rulemaking for manufacturers. Airbus said that the cost
of future LOV extensions should be included. Based on further
discussion to identify these costs, Airbus and the FAA agreed that
Airbus currently meets the intent of today's rule by performing an
evaluation of structure susceptible to fatigue and establishing an LOV
prior to the development of WFD. The rule does not require
manufacturers to extend LOVs--thus these extensions are not a
compliance cost. The FAA does understand that LOV extensions are part
of the existing Airbus business practice.
    Boeing stated that the most significant costs will be borne by the
manufacturer rather than the operator. When the manufacturer has to
perform additional fatigue testing to substantiate an operational
limit, said the commenter, the costs could be quite significant. Based
on further discussion to identify these costs, Boeing and the FAA
agreed that, because Boeing is also already engaged in the activities
required by this final rule, its additional costs will be minimal.
    A later Boeing comment, however, said that the regulatory
evaluation summarized in the Technical Document, which was developed by
the FAA for the public meeting, does not identify future expenses the
Boeing Company will incur. Boeing believes this discounting is not
correct because the company still has substantial work to do in
providing maintenance programs for repairs and alterations, and in
developing LOVs and supportive maintenance actions for post-Amendment
25-45 airplanes. Boeing said that the costs of an airworthiness
directive are being attributed to operators, but do not account for
manufacturers' costs. A second point made by this commenter was that
certain LOVs may be set at a point lower than hoped, simply because the
maintenance actions needed to bring that LOV out to a more distant
point may be too technically difficult and costly to perform. This
could result in a considerable amount of engineering work for Boeing to
develop the LOV that, because the maintenance actions are never
released, might not result in recompense for Boeing. Boeing said that
we are presenting costs as either voluntary compliance for setting LOVs
or as airworthiness directive costs for developing maintenance actions.
    In discussions, Boeing has informed us that the company will
voluntarily do this work to address WFD in its airplanes, with or
without the rule. As a result, the rule does not impose costs, and the
regulatory evaluation properly does not assign costs to Boeing's
voluntary compliance. The rule does not require that design approval
holders develop maintenance actions to be performed to support the LOV,
nor does the rule require development of LOVs for repairs, alterations,
and modifications. If the LOV developed by the design approval holder
does specify maintenance actions, the FAA will separately estimate the
costs of those

maintenance actions at the time as part of the airworthiness directive
notice. Any work done on repairs, alterations, and modifications,
because it is not required by the rule, is not accounted for as a cost
of the rule. Compliance costs are assumed to be borne by the operators.
If manufacturers have incurred costs in developing the maintenance
actions for operators to reach LOV, there is nothing that precludes
them from being recompensed for that work. The FAA based the analysis
of costs in our Initial Regulatory Evaluation on discussions with the
AAWG. Because this final rule is significantly different from the NPRM,
the agency has re-evaluated these costs, and the results are reflected
in the Final Regulatory Evaluation.
d. Cost of Failing To Harmonize Rule
    Industry representatives on the AAWG, Airbus, Boeing, and the ATA
pointed out that the regulatory evaluation did not consider the cost of
failing to harmonize the rule with other airworthiness authorities.
Commenters suggested that--if the rule were not harmonized--there would
be a substantial negative economic impact with respect to the transfer,
lease, or sales of airplanes between the U.S. and other countries.
Commenters suggested that bilateral agreements be amended to support
the transfer of used airplanes subject to this final rule.
    As discussed in section III.K. above, the FAA is working closely
with EASA and other national airworthiness authorities to harmonize
this final rule as much as possible. Many of the changes to the
proposed rule will facilitate such harmonization.
e. Cost To Replace an Airplane
    A number of commenters said that the initial regulatory evaluation
used replacement costs that are not accurate or justified. According to
the ATA, ``The assumptions used in the regulatory evaluation ignore the
reality that some airlines replace their fleets with new aircraft in
most cases, while others (particularly cargo carriers) depend on used
aircraft with long remaining lives to support their particular business
case.'' In a related vein, Airbus, the ATA, and an individual commenter
said that the regulatory evaluation failed to consider the significant
cost to operators of retiring airplanes. Of particular concern was the
situation where airplanes that support an operation reach their
operational limit, and there are no new airplanes which could fill the
same role. The ATA said that the regulatory evaluation ignores factors
that operators would take into account when deciding whether to retire
an airplane or to seek approval of an extended operational limit but
did not define those factors.
    In the public meeting on December 11, 2008, a commenter
representing United Parcel Service noted that the cost benefit analysis
was based only on Boeing airplanes, and said that if the Airbus
airplanes were included, there would be one airplane model with an LOV
that is actually less than the design service goal in the original
NPRM. United Parcel Service commented that operators of those airplanes
would be interested in understanding how that economic impact to the
residual value of those airplanes was not included in the cost. United
Parcel Service also asked, since Boeing had expressed discomfort with
the use of the anticipated LOV information that it had originally given
the FAA, how the FAA could be comfortable using that information for
the regulatory evaluation. Since the public meeting, Boeing has
provided updated information about anticipated LOVs for their
airplanes. Airbus has provided a table containing updated information
on certain Airbus model LOVs and anticipated extensions to LOVs. The
FAA uses this updated information in the Final Regulatory Evaluation.
    Lynden Air Cargo said that the initial regulatory evaluation did
not provide a true economic impact for either design approval holders
or operators because it is based upon unknown facts from too few design
approval holders and with no input from operators, who will bear 90% of
the costs. Lynden Air Cargo provided flight cycle and flight hour data
for its L-382G airplanes. Based on an LOV of 75,000 flight hours,
Lynden Air Cargo stated that issuance of the ``anticipated LOVs,''
which are included in the Technical Document, would require that Lynden
Air Cargo immediately retire three of its six airplanes and, at the
Lynden Air Cargo current utilization rate, retire the other three by
approximately December 2019. Lynden Air Cargo estimates the cost to
replace its six airplanes would range from $120 million to $810
million, if comparable airplanes were available.
    Lockheed indicated that the LOV anticipated for the L-382 would be
based only on flight hours. Based on flight hours, usage, and current
ownership, we do not estimate that any L-382 airplanes will be retired
in our 20-year analysis period. Lockheed stated that it will continue
to support the L-382 model regardless of whether the FAA issues a WFD
rule.
    In developing the Final Regulatory Evaluation, the FAA used a
commercial fleet data product that identifies the status of airplane
hours and cycles. The FAA found only one U.S.-registered airplane
currently operating under part 121 with a number of flight cycles
exceeding the anticipated LOV for the airplane and only five U.S.-
registered airplanes operating under part 121 that exceed 80% of those
LOVs.
    The economic cost of requiring retirement of an airplane at the
anticipated LOV is a central issue in the cost estimate for today's
rule. Common business practice is to value assets at the current market
value, and the FAA follows this practice in the Final Regulatory
Evaluation. In the case of airplanes at or near the end of their
commercial lives, this value is quite small. Assigning a cost of
purchasing a new airplane to replace an airplane at LOV would be a
serious overstatement because it ignores the decline in value as
airplanes age.
f. Residual Value of Airplanes
    Several commenters, including the ATA, FedEx, United Parcel
Service, Airbus, the CAA, Technical Data Analysis, Inc., and Celeris
Aerospace of Canada, stated that the initial regulatory evaluation did
not consider the impact of the proposal on loans, leases, and residual
value of airplanes. They said the rule would have a particularly
significant effect on cargo operations, which tend to use older
airplanes.
    These comments are based on an assumption that LOVs will be
established at levels below where significant numbers of airplanes
would otherwise be retired.
    As discussed previously, the vast majority of airplanes are
currently retired well before the LOVs that design approval holders
anticipate establishing under this final rule. These retirements are
for economic reasons unrelated to today's rule. The FAA expects that
future retirement decisions will be made for similar reasons and that
this final rule will force retirement of only one airplane that is
otherwise reaching the end of its commercial operational life.
    We use an appraiser-estimated airplane value when the airplane
reaches LOV before retirement. This estimate properly reflects the true
value of the asset. To include any other cost estimate would be double
counting.
3. ``Rotable'' Parts
    Northwest Airlines commented that it is not clear whether or not
airplane life limits (the commenter's term for LOVs) extend to
components, such as engine nacelles, passenger and cargo doors, flight
controls, and wing-to-body fairings. These components can be

``swapped out,'' or rotated (they're known in the industry as rotable
parts) from one airplane to another. Northwest Airlines said that there
is a potential for significant costs associated with rotable parts if
they are limited by an airplane's LOV. Operators typically do not track
the number of accumulated flight cycles or flight hours for them.
Northwest Airlines stated that operators may have to assume the flight
cycles or flight hours on affected rotable parts to be equal to the
world high-time airplane for that model. This may require that
operators ground many airplanes or scrap rotable parts, resulting in
significant costs that have not been captured in the regulatory
evaluation included in the Technical Document.
    The LOV is an airplane-level number. The FAA does not anticipate
that rotable parts will be identified by design approval holders as
structure susceptible to WFD. This is because the parts typically
considered as rotable do not have structural details and elements that
are repeated over large areas and operate at the same stress levels. AC
120-YY provides examples of structure in which multiple site damage or
multiple element damage could occur. Rotable parts are not included in
those examples. As a result, we have determined that rotable parts do
not affect the cost of this final rule.
4. Use of LOVs for Financial Evaluations
    Airbus expressed concerns similar to those expressed by Boeing and
the members of AAWG about lack of uniformity in the manner in which
various manufacturers are setting LOVs. The commenter also stated that
it was important that the LOVs, and the LOV flight hour or flight cycle
numbers, not be used by non-technical people in the finance community
to set depreciation schedules, commercial valuations, comparisons, and
competitive arguments. Airbus was concerned that such use of non-
standardized data could lead to market distortion.
    Airbus requested that we not publish LOV tables for each
manufacturer's product lines in the rule and its preamble. It stated
that this information would much more appropriately be published and
updated in the manufacturer's Instructions for Continued Airworthiness
for each airplane. Airbus suggested that, if the FAA nevertheless
decides that publishing such LOV tables is necessary, then it would be
important to develop, in concert with industry, the definitions,
criteria, and methodologies to be used, so that resulting LOVs from all
sources are consistent.
    The FAA has revised the rule to ensure that there is an objective,
performance-based standard for developing LOVs, and AC 120-YY has been
updated to provide guidance in complying with those standards. The
reason that design approval holders may appear to be arriving at
different LOV numbers is largely a function of the age of their
respective fleets. A design approval holder whose fleet is older will
have a much larger body of service experience on which to confidently
base an LOV. A design approval holder with a younger fleet might be
more conservative when first setting an LOV, because there is not as
much service experience data on which to base it. Another factor
affecting how a design approval holder goes about setting an LOV is how
much fatigue testing has been performed on a particular model.
    The FAA appreciates that Airbus supports the intent of the WFD
rulemaking, and understands Airbus' concern that LOVs could be
misinterpreted by those who ``set or approve'' the economic life of an
airplane. The FAA does not expect, nor intend, the LOV in the WFD final
rule to set the economic life of an airplane. The March 18, 2009
edition of Aviation Daily reported that Airbus has extended the service
goals of the A330-200 and A340-200 and -300. The purpose of publishing
manufacturers' LOVs in the regulatory evaluation appendix is to provide
clarity, transparency, and reproducibility for the economic analysis.
As Airbus requested, the reason for the publication of LOVs is
clarified in the Final Regulatory Evaluation. In the regulatory
evaluation, the FAA states that it is important to note that
manufacturers have changed LOVs based on updated information. Airbus,
for instance, sets an initial LOV as a declared point for certification
purposes. Periodically, as airplanes are shown to be viable for longer
lives, design approval holders put programs in place to extend LOVs
well before those utilizations are achieved. The FAA believes that
manufacturers will continue this practice into the future and update
their airplanes' LOVs. Thus the LOVs used in this regulatory evaluation
should not be used as a basis for setting the economic life of an
airplane. Based upon history, our estimated costs, which were based
upon the current LOVs, may be overstated.

IV. Regulatory Notices and Analyses

Paperwork Reduction Act

    The Paperwork Reduction Act of 1995 (44 U.S.C. 3507(d)) requires
that the FAA consider the impact of paperwork and other information
collection burdens imposed on the public. According to the 1995
amendments to the Paperwork Reduction Act (5 CFR 1320.8(b)(2)(vi)), an
agency may not collect or sponsor the collection of information, nor
may it impose an information collection requirement, unless it displays
a currently valid Office of Management and Budget (OMB) control number.
    This final rule will impose the following new information
collection requirements. As required by the Paperwork Reduction Act of
1995 (44 U.S.C. 3507(d)), the FAA has submitted these information
collection amendments to OMB for its review. The Office of Management
and Budget approved these new information collection requirements
associated with this final rule and assigned OMB Control Number 2120-
0743.
    Title: Widespread Fatigue Damage.
    Summary: Today's rule consists of regulatory changes pertaining to
widespread fatigue damage in transport category airplanes. Some of
these changes require new information collection. The new information
requirements and the persons required to provide that information are
described below.
    (1) Amendment of part 26 requires that holders of design approvals
for certain existing transport category airplanes establish limits of
validity (operational limits) for those airplanes. Those design
approval holders are also required to revise the Airworthiness
Limitations section of the Instructions for Continued Airworthiness
(ICA) to include the LOV.
    (2) Amendment of part 26 also requires that design approval holders
submit to the FAA a plan detailing how they intend to comply with the
new requirements. The compliance plan ensures that design approval
holders fully understand the requirements, correct any deficiencies in
planning in a timely manner, and provide the information needed by the
operators for timely compliance with the rule.
    (3) Any person operating an airplane under part 121 or 129 is
required to revise its maintenance program to incorporate an
Airworthiness Limitations section that includes an LOV. Operators would
be prohibited from operating an airplane past that limit.
    (4) As an option, any person may apply for an extended LOV for
affected airplanes. This option has requirements similar to those
imposed on design approval holders for establishing an initial LOV.
There may be service information developed that would

support the extended limit and would be documented as airworthiness
limitation items. To operate beyond the initial LOV, an operator would
have to incorporate the extended limit and any airworthiness limitation
items pertaining to widespread fatigue damage into its maintenance
program.
    Use of Collected Information: These requirements support the
information needs of the FAA in finding compliance with the rule by
design approval holders and operators.
    Average Annual Burden Estimate: The burden would consist of the
work necessary to:
     Develop or revise the Airworthiness Limitations section of
the Instructions for Continued Airworthiness to include the LOV.
     Develop the compliance plan.
     Incorporate the new information into the operator's
maintenance program.
    Today's rule results in the following annual recordkeeping and
reporting burden:

                               Figure 4--Recordkeeping and Reporting for This Rule
----------------------------------------------------------------------------------------------------------------
                                                                                Present value
  Documents required to show compliance with the proposed rule      Total labor    Total average    discounted
                                                                       hours       annual hours    ($2010) cost
----------------------------------------------------------------------------------------------------------------
FAA-approved revised or new ALS.................................             660             132         $41,674
FAA-approved WFD compliance plan................................             435           * 435          33,418
FAA-approved maintenance program revision for operators.........             210              35          12,846
                                                                 -----------------------------------------------
    Total.......................................................           1,305             602          87,938
----------------------------------------------------------------------------------------------------------------
* This one-time burden will occur in the first 90 days of the compliance period.

    The FAA computed the annual recordkeeping burden (in total hours)
by analyzing the paperwork needed to satisfy each requirement of the
rule. The average cost per hour varies with the number of affected
airplanes in each group, the amount of engineering time required to
develop the LOV, and the amount of time required for revising the
Airworthiness Limitations section of the Instructions for Continued
Airworthiness. Other costs associated with the information collection
requirements within this rule (in addition to the monetized hourly
costs reflected above) are minimal.
    In addition to the requirements outlined above, future applicants
for either supplemental type certificates or amendments to type
certificates that decrease or increase maximum takeoff gross weights
would be required to develop a compliance plan for the certification
project. The Paperwork Reduction Act compliance for development of
these certification plans is covered by a previously approved
collection (OMB Control Number 2120-0018) associated with part 21. We
estimate the additional burden to include information on a plan for
establishing an LOV for these airplanes would be minimal.

International Compatibility

    In keeping with U.S. obligations under the Convention on
International Civil Aviation, it is FAA policy to comply with
International Civil Aviation Organization (ICAO) Standards and
Recommended Practices to the maximum extent practicable. The FAA has
determined that there are no ICAO Standards and Recommended Practices
that correspond to these regulations.

Economic Assessment, Regulatory Flexibility Determination, Trade Impact
Assessment, and Unfunded Mandates Assessment

    This portion of the preamble summarizes the FAA's analysis of the
economic impacts of this Final Rule. It also includes the final
regulatory flexibility determination, the international trade impact
assessment, and the unfunded mandates assessment. The FAA suggests
readers seeking greater detail read the full regulatory evaluation, a
copy of which has been placed in the docket for this rulemaking.
    Changes to Federal regulations must undergo several economic
analyses. First, Executive Order 12866 directs that each Federal agency
shall propose or adopt a regulation only upon a reasoned determination
that the benefits of the intended regulation justify its costs. Second,
the Regulatory Flexibility Act of 1980 requires agencies to analyze the
economic impact of regulatory changes on small entities. Third, the
Trade Agreements Act (19 U.S.C. 2531-2533) prohibits agencies from
setting standards that create unnecessary obstacles to the foreign
commerce of the United States. In developing U.S. standards, this Trade
Act requires agencies to consider international standards and, where
appropriate, to be the basis of U.S. standards. Fourth, the Unfunded
Mandates Reform Act of 1995 (Pub. L. 104-4) requires agencies to
prepare a written assessment of the costs, benefits, and other effects
of proposed or final rules that include a Federal mandate likely to
result in the expenditure by State, local, or Tribal governments, in
the aggregate, or by the private sector, of $100 million or more
annually (adjusted for inflation).
    In conducting these analyses, FAA has determined this final rule
has benefits that justify its costs, and is a ``significant regulatory
action'' as defined in section 3(f) of Executive Order 12866 because it
raises novel policy issues contemplated under that executive order. The
rule is also ``significant'' as defined in DOT's Regulatory Policies
and Procedures. The final rule, if adopted, however, will not have a
significant economic impact on a substantial number of small entities,
will not create unnecessary obstacles to international trade and will
not impose an unfunded mandate on State, local, or Tribal governments,
or on the private sector. These analyses, available in the docket, are
summarized below.

Total Costs and Benefits of This Rulemaking

    The overriding safety concern of today's rule is WFD-related
incidents and accidents that have occurred and the continuing
discoveries of WFD problems in the fleet. The current approach does not
always find WFD before in-flight events occur. Today's rule will
establish the necessary steps to prevent WFD in the future by requiring
that design approval holders establish LOVs.
    With this final rule, design approval holders may continue their
work to provide maintenance actions that support the safe operation of
airplanes up to LOV. The FAA would proactively issue airworthiness
directives mandating those planned maintenance actions rather than
reactively issuing emergency airworthiness directives and immediately
adopted rules which

require unanticipated inspections and repairs. The FAA estimates that
this approach is worth $4.8 million in present value.
    In contrast to the NPRM, the final rule total costs are minor.
Several significant factors are responsible for the reduction in these
costs. First, the final rule does not include the repair, alterations,
and modification requirement as in the NPRM. Second, many older
airplanes have been retired since the NPRM. Third, due to the comments
and conversations with design approval holders, the agency now
understands that most LOVs will be set 33% to 180% higher than design
service goal rather than at design service goal as was specified in the
NPRM. Because of current maintenance programs and voluntary compliance
by design approval holders, costs for design approval holders and
operators are expected to be minimal. We anticipate that today's rule
will result in one airplane retiring sooner than the operator would
like, in contrast to the NPRM which predicted that many airplanes would
retire sooner. Thus our base case model attributes the cost of this
rule to the retirement of that one airplane, because it will reach the
anticipated LOV within the 20-year analysis period. This will result in
costs of $3.8 million, with a present value of $3.6 million.
    Thus, as noted earlier, this final rule's expected present-value
benefits of $4.8 million exceed the expected present-value costs of
$3.6 million.

                        Figure 5--Comparison of Cost Assumptions for NPRM and Final Rule
----------------------------------------------------------------------------------------------------------------
                                                                                Final rule
                                             NPRM present                                         present  value
             NPRM assumptions               value costs ($         Final rule assumptions            costs  ($
                                               millions)                                             millions)
----------------------------------------------------------------------------------------------------------------
Operator Retirement Costs.................             160  Operator Retirement Costs...........             3.6
     Initial Operational Limit                         Limit of validity (LOV) >
     (IOL) = Design Service Goal (DSG).                     DSG for many models
     27 airplanes would be retired                     1 airplane would be
     in the first year of compliance.                       retired in the 20[dash]year analysis
                                                            period
     Some IOL extensions.                              Few LOV extensions
Operator Maintenance Program Costs........             164  Operator Maintenance Program Costs..               0
     WFD maintenance actions \49\                    With higher LOV, WFD
     were included with extended                             maintenance actions may be
     operational limits.                                     necessary and would be mandated by
                                                             ADs, per existing practice.\50\
     We assumed some operators                         Operators' costs to
     would perform maintenance actions.                     perform maintenance actions are
                                                            included in cost of ADs
Design Approval Holder (DAH) Costs........              36  DAH Costs...........................               0
    Assumed 10% of entire costs.                              Assumed minimal costs because DAHs
                                                            are voluntarily developing LOVs and
                                                            maintenance actions
                                           ----------------                                      ---------------
        Total Costs.......................             360    Total Costs.......................             3.6
----------------------------------------------------------------------------------------------------------------

Who is potentially affected by this rulemaking?

     Design approval holders of transport category airplanes
with a maximum takeoff gross weight greater than 75,000 pounds.
---------------------------------------------------------------------------

    \49\ Maintenance actions include inspections, modifications, and
replacements. Because the extended LOV is not required, operators
would have to decide to retire airplanes or perform the maintenance
actions with the extended LOV.
    \50\ These ADs would be issued eventually, even without this
rule, because WFD is inevitable and is an unsafe condition. More ADs
may need to be written without this rule. If the necessary service
information is not developed until after a finding of WFD in
service, the resulting ADs are likely to include interim action
requirements and have shorter compliance times, as compared with ADs
issued based on service information developed as required by this
rule.
---------------------------------------------------------------------------

     Applicants for type certificates of transport category
airplanes with a maximum takeoff gross weight greater than 75,000
pounds, if the date of application was before the effective date of the
rule.
     Applicants for amendments to type certificates of
transport category airplanes with a maximum takeoff gross weight
greater than 75,000 pounds, with the exception of those that change the
maximum takeoff gross weight of the airplane.
     Applicants or design approval holders for either
supplemental type certificates or amendments to type certificates that
increase maximum takeoff gross weights from 75,000 pounds or less to
greater than 75,000 pounds.
     Applicants or design approval holders for either
supplemental type certificates or amendments to type certificates that
decrease maximum takeoff gross weight from greater than 75,000 pounds
to 75,000 pounds or less after the effective date of the rule.
     Applicants for future type certificates, or for either
supplemental type certificates or amendments to future type
certificates, for all transport category airplanes, after the effective
date of the rule.
     U.S. certificate holders and foreign air carriers and
foreign persons operating U.S.-registered transport category airplanes
under 14 CFR part 121 or 129 with a maximum takeoff gross weight
greater than 75,000 pounds.
     Operators of any transport category airplanes certified in
the future, regardless of maximum takeoff gross weight, if the date of
application was after the effective date of the rule.

Our Cost Assumptions and Sources of Information

     Discount rate = 7%.
     Period of Analysis = 20 years.
     Value of fatality averted = $5.8 million (Source: U.S.
Department of Transportation, Treatment of Value of Life and Injuries
in Preparing Economic Evaluations, February 8, 2008).
     Aircraft Values = 2009 Avitas Blue Book of Jet Aircraft/
Industry Consultation.
     Aircraft Fleet Data = OAG Associates Fleet Database.

Alternatives Considered

    The FAA considered four alternatives to the proposed rule. These
were:
    1. Exclude small entities.
    2. Extend the compliance deadline for small entities.

    3. Establish lesser technical requirements for small entities.
    4. Expand the requirements To cover more airplanes.
1. Exclude Small Entities
    The FAA concluded that excluding small entities from all the
requirements of the proposed rule was not justified. The purpose of the
proposed rule is to maintain the airworthy operating condition of
airplanes regardless of secondary considerations.
2. Extend the Compliance Deadline for Small Entities
    The FAA also considered options that would lengthen the compliance
period for small operators. The FAA believes time extensions only
provide modest cost savings and leave the system safety at risk.
3. Establish Lesser Technical Requirements for Small Entities
    The FAA considered establishing lesser technical requirements for
small entities. However, the FAA believes the risks are similarly
unreasonable for small entities operating airplanes susceptible to WFD,
and that the benefits of including small entities justify the cost.
4. Expand the Requirements To Cover More Airplanes
    The FAA considered requiring all operators of existing transport
category airplanes to comply with the proposed rule. However, the
overwhelming majority of passengers and cargo are carried by airplanes
with a maximum gross takeoff weight of greater than 75,000 pounds. The
75,000 pound weight cutoff was based on recommendations from the AAWG
for WFD rulemaking. Because of this, the FAA decided to restrict
compliance to operators of those airplanes.
    The FAA concludes the current rule is the preferred alternative
because it has benefits exceeding compliance costs and allows for
continued operation of certain airplanes only up to the point where
existing maintenance actions can no longer ensure that the airplanes
are free from WFD.

Benefits of This Rulemaking

    The non-quantified benefits include the safe (from WFD) operation
of airplanes up to the LOV.
    The lower-bound present value benefits of this final rule (the
minimum value of a range estimate of benefits) are $4.8 million in
present value. These quantified benefits are based on the near
elimination of emergency airworthiness directives.

Costs of This Rulemaking

    The total incremental costs of this final rule are approximately
$3.6 million in present value from the costs of retiring one airplane.

Final Regulatory Flexibility Analysis

Introduction and Purpose of This Analysis
    The Regulatory Flexibility Act of 1980 (Pub. L. 96-354) (RFA)
establishes ``as a principle of regulatory issuance that agencies shall
endeavor, consistent with the objectives of the rule and of applicable
statutes, to fit regulatory and informational requirements to the scale
of the businesses, organizations, and governmental jurisdictions
subject to regulation. To achieve this principle, agencies are required
to solicit and consider flexible regulatory proposals and to explain
the rationale for their actions to assure that such proposals are given
serious consideration.'' The RFA covers a wide range of small entities,
including small businesses, not-for-profit organizations, and small
governmental jurisdictions.
    Agencies must perform a review to determine whether a rule will
have a significant economic impact on a substantial number of small
entities. If the agency determines that it will, the agency must
prepare a regulatory flexibility analysis as described in the RFA.
    However, if an agency determines that a rule is not expected to
have a significant economic impact on a substantial number of small
entities, section 605(b) of the RFA provides that the head of the
agency may so certify and a regulatory flexibility analysis is not
required. The certification must include a statement providing the
factual basis for this determination, and the reasoning should be
clear.
    The FAA considers that this final rule will not result in a
significant economic impact on a substantial number of small entities.
The purpose of this analysis is to provide the reasoning underlying the
FAA determination.
    First, we will discuss the reasons why the FAA is considering this
action. We will follow with a discussion of the objective of, and legal
basis for, the final rule. Next, we explain there are no relevant
Federal rules which may overlap, duplicate, or conflict with the final
rule. Then we will discuss the substantial changes from the proposed to
the final rule. Next, we will discuss the comments received about the
Initial Regulatory Flexibility Analysis (IRFA). Lastly, we will
describe and provide an estimate of the number of small entities
affected by the final rule and why the FAA considers that this final
rule will not result in a significant economic impact on a substantial
number of small entities.
    We now discuss the reasons why the FAA is considering this action.
    The FAA is issuing this final rule to address the structural
problems of aging airplanes known as ``widespread fatigue damage''
(WFD). WFD is characterized by the simultaneous presence of cracks at
multiple structural locations that are of sufficient size and density
that the structure will no longer meet its residual strength
requirement and could catastrophically fail.
    Past examples of WFD occurring in the fleet include:
     The 1988 Aloha 737 accident,
     An in-flight Lockheed Model L-1011 failure of aft pressure
bulkhead stringer attach fittings,
     A McDonnell Douglas Model DC-9 aft pressure bulkhead
cracks,
     Boeing Models 727 and 737 lap splice cracking,
     Boeing Model 767 aft pressure bulkhead cracking, and
     Boeing Model 747 and Airbus A300 frame cracking.
    Because of these past incidents, accidents, and inspection
discoveries and others, the FAA has already issued about 100 WFD-
related airworthiness directives.
    This final rule is being promulgated because the FAA believes the
risk of an accident caused by WFD, and the potential collateral damage
after such an accident, is too high without implementing today's rule.
    We now discuss the objective of, and legal basis for, the final
rule. Next, we discuss if there are relevant Federal rules which may
overlap, duplicate, or conflict with the final rule.
    Title 49 of the United States Code requires the FAA Administrator
to consider the following authority:
     Assigning, maintaining, and enhancing safety and security
as the highest priorities in air commerce. (49 U.S.C. 40101(d)(1).
     Aging Airplane Safety Act of 1991. (49 U.S.C. 44717).
     The FAA Administrator's statutory duty to carry out his or
her responsibilities ``in a way that best tends to reduce or eliminate
the possibility or recurrence of accidents in air transportation.''
(See 49 U.S.C. 44701(c)).
    Therefore, this final rule will amend Title 14 of the Code of
Federal Regulations to require existing design approval holders to
establish LOVs and operators of any affected airplane to incorporate
those LOVs into maintenance programs of large transport

category airplanes with a maximum takeoff gross weight greater than
75,000 pounds, operating under 14 CFR part 121 and 129. These
requirements will also apply to all applicants for type certificates
after the effective date of the rule and operators of those airplanes.
Today's rule does not require that any maintenance actions be performed
to prevent WFD before an airplane reaches its LOV. Any maintenance
actions necessary to reach the LOV will be mandated by airworthiness
directives through separate rulemaking actions, so their costs are not
attributable to this final rule.
    This final rule will not overlap, duplicate, or conflict with
existing Federal Rules.
    We now discuss the changes from the proposed to the final rule and
the reason the small entity determination in the Final Regulatory
Flexibility Analysis (FRFA) has changed.
    The FAA has made substantial changes to the WFD NPRM that
significantly reduces costs to both small and large business entities.
We have eliminated the requirement to evaluate WFD associated with
repairs, alterations, and modifications of the baseline airplane
structure, except for those mandated by airworthiness directives. This
change dramatically reduces the economic impact of the NPRM's estimated
compliance costs to small entity operators of part 25 airplanes. Also,
in our request for comments, design approval holders responded by
providing estimates of LOVs for their affected airplanes. In the NPRM
we assumed the LOV will occur at an airplane's design service goal.
Based on design approval holder comments LOV, in many cases, occurs
anywhere from 33% to 180% beyond the design service goal, depending on
the equipment model. An operator can now operate an airplane well past
its design service goal and not incur the costs of making the decision
to retire or extend the affected airplane's LOV until much later in the
airplane's life. The only remaining cost is that we assume operators
will retire their airplanes at LOV, rather than incurring the cost of
the additional maintenance actions that may be needed for an extended
LOV. With the scope of the rule reduced, both in terms of required
inspections and in terms of affected airplanes, the economic costs of
this final rule are much lower than the costs estimated in the NPRM and
in the initial regulatory evaluation.
    The FAA will now discuss the one comment received about the Initial
Regulatory Flexibility Analysis (IRFA).
    In the responses to the IRFA of the NPRM, we received a comment
from Lynden Air Cargo. Lynden stated its L-382G airplanes were not
included in IRFA. The commenter is correct. The Fleet data services
consulted for the initial regulatory evaluation did not carry flight
utilization data for L-382Gs, and the FAA was unable to determine the
number of accumulated flight cycles or flight hours of Lynden's fleet
in comparison to the anticipated LOV for those airplanes. Because of
the lack of utilization data, Lynden's fleet was not included in our
sample for the IRFA analysis. Lynden Air Cargo has since provided the
FAA with utilization information for its L-382G fleet. Lockheed has
provided an updated anticipated LOV for the L-382G fleet, based just in
hours, and Lynden's entire fleet is below 80% of the LOV. With the base
hours less than 80% of LOV, and with the current utilization rates of
these airplanes, they will not reach LOV in the 20-year analysis time
frame. Therefore the FAA expects no economic impact to Lynden Air Cargo
in the analysis period for the final rule.
    The FAA will now discuss the methodology used to determine the
number of small entities for which the final rule will apply. The FAA
will also discuss why the agency considers that this final rule will
not result in a significant economic impact on manufacturers of part 25
airplanes.
    For aircraft operators and manufacturers, a small entity is defined
as one with 1,500 or fewer employees.\51\ Since there are operators
that met those criteria, the FAA conducted an economic impact
assessment to determine if the rule will have a significant economic
impact on a substantial number of these operators.
---------------------------------------------------------------------------

    \51\ 13 CFR 121.201, Size Standards Used to Define Small
Business Concerns, Sector 48-49 Transportation, Subsector 481 Air
Transportation.
---------------------------------------------------------------------------

    This final rule will become fully effective in 2010. Although the
FAA forecasts traffic and air carrier fleets to 2030, too many factors
are in play to estimate a future number of small entities, determine if
an operator will still be in business, or determine whether that
operator will still remain a small business entity. Therefore the
agency will use the current U.S. operator's fleet and employment in
order to determine the number and impact on small business entities
this final rule will affect.
    For analysis purposes, the FAA has divided the small entities that
might be impacted by this final rule into two major classes, airplane
manufacturers and air carriers.
    Currently, U.S. part 25 aircraft manufacturer type certificate
holders include the following:
     The Boeing Company.
     Cessna Aircraft Company (a subsidiary of Textron Inc.).
     Raytheon Company.
     Gulfstream Aerospace Corporation (a wholly owned
subsidiary of General Dynamics).
    All United States part 25 aircraft manufacturers exceed the Small
Business Administration small-entity criteria of 1,500 employees for
aircraft manufacturers.
    Air carriers potentially affected by the final rule include
operators engaged in the following:
     Scheduled air transportation.
     Air courier service.
     Nonscheduled air transportation.
    The FAA obtained the number of U.S.-operated airplanes having a
maximum takeoff gross weight greater than 75,000 pounds from the OAG
Associates Fleet Database (March 2009). This database identifies U.S.
operators of affected airplanes by providing airplane age and flight
utilization statistics. The FAA used the airplane flight utilization
information in the analysis of small entity operator's airplanes
affected by this WFD final rule. The FAA obtained annual operators'
revenue and employment data from current public filings, the World
Aviation Directory, and U.S. DOT Form 41 schedules.
    Companies with greater than 1,500 employees were excluded from
further analysis. Operators in Chapter XI bankruptcy were also
excluded, since the outcomes of such proceedings are unknown. Lastly,
we excluded all part 25 turbine-powered airplanes with a maximum
takeoff gross weight of 75,000 pounds or less, or with a type
certificate issued before January 1, 1958, because these airplanes are
not affected by the final rule.
    This procedure resulted in a list of airplanes, operated by U.S.
operators with less than 1,500 employees, with a gross takeoff weight
greater than 75,000 pounds. To this database were added airplane-
specific design service goals, LOVs, and airplane residual value
fields. The FAA used the design service goals published in the WFD NPRM
and later updated them based on FAA and industry input. Manufacturers
provided the LOVs. Airplane residual values were obtained from the 2009
Avitas Bluebook of Jet Aircraft and consultations with industry.
    Next follows the discussion of the number of small entity operators
with airplanes affected by the rule, and how

much it will cost for them to be in compliance.
    Today's rule may cause airplanes to be retired, sold, or replaced
sooner than an operator would like. Companies make decisions on the
retirement, sale, or replacement of airplanes for many reasons. The
decision point to sell, retire, or replace an airplane differs across
companies. Operators take into account several key factors in their
decision on when to retire an aircraft. The following are some of those
key factors:
     Maintenance costs.
     Noise levels.
     Fuel consumption.
     Loss of consumer demand.
     Regulation changes.
     Shifting operator business plans.
     Operating costs.
    Therefore, a company generally decides to retire, sell, or replace
an airplane long before its LOV is reached. Given current airplane
utilization rates, the FAA does not expect the final rule to affect
companies below 75% of an airplane's LOV. When an airplane's flight
utilization (measured in flight cycles or hours) exceeds 75% of LOV,
the expectation is that the WFD provisions will become an increasingly
important component of the decision to retire the airplane. All U.S.
airplanes over 75% LOV currently operated by small business entities
are in non-scheduled service. Many of these affected airplanes are
being operated by cargo operators and hence have a lower utilization
rate than their counterparts in scheduled passenger service.
    The FAA discovered that 21 airplanes being operated by eight small
entities were over 75% of LOV. For the 21 affected airplanes over 75%
of LOV, the FAA analyzed utilization history reports by serial number.
Results of this analysis showed that saying that 21 airplanes are over
75% of their LOVs overstates the number of airplanes affected by this