---------------------------------------------------------------------------

    \58\ See Folkard, supra note 15, at 98.
---------------------------------------------------------------------------

    Turning to the concerns expressed by industry commenters, the FAA
notes that air carriers currently utilize schedules that are
unrealistically optimistic and do not include sufficient buffers for
unforeseen circumstances. It has been the FAA's experience that an air
carrier subject to an 8-hour scheduled flight-time limit will sometimes
schedule a flight that, on paper, lasts 7 hours and 59 minutes when the
air carrier knows that the actual flight will likely take well over 8
hours to complete. Because many current air carrier schedules are
unreasonably optimistic, air carriers can prevent many of the pre-
takeoff situations listed in their comments simply by incorporating
reasonable buffers for unforeseen circumstances into their scheduling
practices.
    However, in evaluating the above comments, the FAA noted that
different considerations apply after an aircraft has taken off. If
unexpected circumstances significantly increase the length of the
flight while an aircraft is in the air, the only way for a flightcrew
member to comply with the flight-time limits imposed by this rule would
be to conduct an emergency landing instead of piloting the aircraft to
its intended destination. Because this is not the preferred method of
complying with flight-time limits, the FAA has amended this section to
provide a post-takeoff flight-time extension to the extent necessary to
safely land the aircraft at its intended destination airport \59\ if
unexpected circumstances occur after takeoff. To monitor the use of
this post-takeoff extension, the FAA is requiring certificate holders
to report their flightcrew members who exceed the flight-time limits
and describe the circumstances surrounding the exceeded flight
time.\60\
---------------------------------------------------------------------------

    \59\ If the destination is unavailable, the aircraft would land
at the designated alternate airport.
    \60\ The ``FDP Extensions'' section contains a more detailed
discussion of the reporting requirements that apply to flightcrew
members who exceed the applicable FDP and/or flight-time limits.
---------------------------------------------------------------------------

    The FAA emphasizes that this extension only applies to unexpected
circumstances that arise after takeoff. If a flightcrew member becomes
aware, before takeoff, that he or she will exceed the applicable
flight-time limit, that flightcrew member may not take off, and must
return to the gate.
    One hundred sixty-seven individual commenters opposed increasing
the augmented flight-time limit to 16 hours. AMA supported the 16-hour
flight-time limit for augmented operations, stating that peer review
studies and SAFTE/FAST modeling show that after 16 hours on duty crew
performance falls off dramatically.\61\ NJASAP stated that flight-time
limitations are necessary for augmented operations, and that use of an
FRMS to extend maximum flight times should be subject to high levels of
scrutiny and oversight. Conversely, Continental asked that augmented
FDPs be allowed to exceed the 16-hour flight-time limit. Atlas Air
stated that, for some augmented FDPs, the 16-hour FDP flight time would
exceed the applicable FDP limit.
---------------------------------------------------------------------------

    \61\ Citing Colquhoun, P., Psychological and Psychophysiological
Aspects of Work and Fatigue, Activitas Nervosa Superior, 1976,
18:257-263.
---------------------------------------------------------------------------

    Continental submitted supplemental comments objecting to the 16-
hour flight time limit for augmented flights. Continental objected to
this limitation on ultra long range (ULR) flights, and it submitted new
studies, which it claimed showed that ULR flights do not pose
additional fatigue risk. ALPA submitted a response to Continental's
supplemental submission, pointing out that ``[f]lights over 16 hours
block conducted by U.S. carriers are rare so there is only limited
actual experience with the fatigue factors of such flights.'' ALPA also
asserted that the studies submitted by Continental were actually a
single study (based on the composition of the subjects), and that the
study suffered from a number of biases, including an age, gender, and
volunteer participation. ALPA also stated that the sample size that the
study examined was too small to provide meaningful data for a system-
wide standard.
    A 16-hour flight-time limit was proposed for augmented operations
because, for a four-pilot crew working in shifts of two, a 16-hour
flight time supposes that each pilot will be at the duty station for
about 8 hours. In response to industry comments, the FAA has concluded
that a slight increase of the limit for four-pilot augmented FDPs would
not impact safety. As such, the augmented flight-time limit for a four-
pilot crew has been increased to 17 hours. Seventeen hours was selected
as the limit because each member of a four-pilot crew that works on a
17-hour flight in shifts of two would only be at the duty station for
8.5 hours. Eight and a half hours of manning the duty station falls
within the 8-to-9-hour flight-time range that, as discussed above, the
FAA considers to be safe.
    Upon reevaluation of the augmented flight-time limit, the FAA has
also concluded that a separate flight-time limit is necessary for a
three-pilot flightcrew. This is because if a three-pilot crew works in
shifts of two on a 17-hour flight, each flightcrew member will be at
the duty station for approximately 11 hours. Because this falls outside
the 8-to-9-hour flight-time range that the FAA considers to be safe,
the flight-time limit for three-pilot augmented flightcrews has been
reduced to 13 hours. A 13-hour flight-time limit ensures that each
member of a 3-pilot crew only needs to be at the duty station for
approximately 8.5 hours.
    Turning to Continental's supplemental comment, as ALPA correctly
pointed out, there are currently very few flights that exceed 16 hours
of flight time, and as such, there is little data concerning the safety
issues presented by these very long flights. The studies put forward by
Continental are not particularly helpful in this regard because they
analyzed a small sample of flights. Due to the small size of this
sample, the data provided by these studies is not sufficient to justify
further increasing the augmented flight-time limits. However, the FAA
may relax the limits for ULR flights (through either an FRMS or a
future rulemaking) if more data is provided showing that longer flight
times do not adversely affect safety.

H. Flight Duty Period--Augmented

    In formulating this rule, the FAA considered the fact that
augmentation is currently used by air carriers to mitigate fatigue. An
augmented flight is staffed by more than the minimally-required number
of flightcrew members, and the extra staffing allows the flightcrew
members to work in shifts and rest during the flight. Existing
regulations allow higher flight times for augmented flights, and this
allows air carriers to conduct longer flights.

    Augmentation has three significant impacts on flight safety. First,
flightcrew members on augmented flights work in shifts, and therefore,
do not spend as much time engaged in the fatiguing task of piloting an
aircraft. For example, on a 17-hour flight staffed by 4 flightcrew
members working in shifts of 2, each flightcrew member will only be on
the flight deck for approximately 8.5 hours. This is in contrast to
unaugmented flights, in which each flightcrew member must be on the
flight deck for the full length of the flight.
    Second, when they are not on the flight deck, flightcrew members on
an augmented flight have access to an onboard rest facility, which will
allow them to sleep during the flight. This in-flight rest will,
depending on the quality of the rest facility, help mitigate against
some of the fatigue accumulated during the FDP. Third, the redundancy
created by augmentation allows fatigued flightcrew members to ask for
assistance from other flightcrew members. Thus, if a flightcrew member
discovers, mid-flight, that he or she is unduly fatigued, that
flightcrew member can ask one of the extra flightcrew members to take
over his or her duties and safely land the aircraft at its intended
destination.
    Because augmentation significantly mitigates fatigue, the FAA has
found that longer FDPs can safely be permitted for augmented flights.
In determining the specific FDP limits, the FAA took note of the
recommendations set out in the TNO Report. The TNO Report was created
to provide science-based advice on the maximum permissible extension of
the FDP related to the quality of the available onboard rest facility
and the augmentation of the flightcrew with one or two pilots. The TNO
Report recommended that: (1) An aircraft with a Class I rest facility
provide an FDP extension equal to 75% of the duration of the rest
period; (2) an aircraft with a Class II rest facility provide an FDP
extension equal to 56% of the duration of the rest period; and (3) an
aircraft with a Class III rest facility provide an FDP extension equal
to 25% of the duration of the rest period.\62\
---------------------------------------------------------------------------

    \62\ TNO Report at 19.
---------------------------------------------------------------------------

    Based on the TNO Report, the FAA proposed Table C, which set out
separate FDP limits for augmented flights. These limits were generally
based on the unaugmented FDP limits, and then were increased in
accordance with the available rest facility by the TNO-Report-
recommended extension. If a flightcrew member was unacclimated, the
augmented FDP limits were reduced by 30 minutes, and the applicable FDP
limits were determined based on the local time at the flightcrew
member's home base. Because augmented FDPs were generally intended to
be used for longer flights, the proposal limited augmented FDPs to
three flight segments. In addition, to ensure sufficient in-flight rest
for augmented flightcrew members, the proposal would have required: (1)
Two consecutive hours of in-flight rest during the last flight segment
for flightcrew members who would be manipulating the controls during
landing, and (2) ninety consecutive minutes of in-flight rest for all
other flightcrew members. The proposal also would have required that at
all times during flight, at least one flightcrew member with a PIC
type-rating must be alert and on the flight deck.
    Drs. Belenky and Graeber stated that ``there is no scientific basis
for the different hours assigned as limits for different departure
times.'' They asserted that ``[u]npublished alertness modeling data
provided to the ATA (and presumably the ARC) demonstrated that a rest
provided during the second half of a long-haul flight equal to (flight
time minus two hours) divided by two produced roughly equivalent
alertness regardless of time of departure.'' Drs. Belenky and Graeber
concluded that, based on the modeling data, there is no need to
differentiate between the different departure times so long as in-
flight rest was provided during the second half of the flight. ATA
added that augmented flights departing later in the day would provide
in-flight sleep during the WOCL for flightcrew members who would be
manipulating the controls during landing, and thus, that in-flight
sleep would be more restful.
    NACA and a number of air carriers who conduct supplemental
operations submitted the following FDP limits as an alternative to the
proposed Table C.

                   NACA Proposed Table C to Part 117--Flight Duty Period: Augmented Operations
----------------------------------------------------------------------------------------------------------------
                                                  Maximum flight duty period (hours) based on rest facility and
                                                                        number of pilots
                                               -----------------------------------------------------------------
                  Acclimated                        Class 1 rest          Class 2 rest          Class 3 rest
                                                      facility              facility              facility
                                               -----------------------------------------------------------------
                                                 3 Pilots   4 Pilots   3 Pilots   4 Pilots   3 Pilots   4 Pilots
----------------------------------------------------------------------------------------------------------------
0000-2359.....................................         18         20         17         19         16         18
----------------------------------------------------------------------------------------------------------------

    The above proposal for augmented operations extends the flight duty
period limits for augmented operations by four to six hours, depending
on the number of pilots used and the type of rest facilities available
onboard the aircraft. Because in-flight rest is provided through
onboard rest facilities, the proposal made by the air carriers who
conduct supplemental operations does not decrease a flightcrew member's
flight duty period limits when the pilot flies during the WOCL.
    UPS suggested that ``four person augmented operations with a class
one rest facility should provide a 16-hour FDP regardless of report
time.'' UPS asserted that this type of augmented FDP limit ``would
allow U.S.-based certificate holders to compete globally without an
FRMS.''
    Atlas Air asserted that most of its augmented flights have FDPs
lasting between 18 and 20 hours, many of which are single-stop and
nonstop flights in support of AMC missions. Atlas Air stated that it
would not be able to keep operating those flights under the limits set
out in Table C. As such, Atlas Air suggested that the FAA increase the
FDP limits in Table C.
    Conversely, ALPA, IPA, CAPA, Flight Time ARC, and other labor
groups submitted the following alternative to the proposed Table C,
arguing that, in applying the TNO Report, Table C utilized a rounding
process ``that doesn't adequately represent the actual calculations
used in the ARC process.''

                      Revised Table C--Flight Duty Period: Acclimated Augmented Flightcrew
----------------------------------------------------------------------------------------------------------------
                                                  Maximum flight duty period (hours) based on rest facility and
                                                                        number of pilots
                                               -----------------------------------------------------------------
          Time of start (local time)                Class 1 rest          Class 2 rest          Class 3 rest
                                                      facility              facility              facility
                                               -----------------------------------------------------------------
                                                 3 Pilots   4 Pilots   3 Pilots   4 Pilots   3 Pilots   4 Pilots
----------------------------------------------------------------------------------------------------------------
0000-0559.....................................      13:50      16:05      12:55      14:20      11:45      12:15
0600-0659.....................................      15:10      17:40      14:10      15:40      12:55      13:25
0700-1259.....................................         16         18      15:25      17:05         14      14:30
1300-1659.....................................      15:10      17:40      14:10      15:40      12:50      13:20
1700-2359.....................................      13:50      16:05      12:55      14:20      11:45      12:15
----------------------------------------------------------------------------------------------------------------

    APA criticized the proposed Table C for not applying the TNO
Report's rationale to the unaugmented FDP limits for the late evening
and early morning hours. APA's alternative to Table C had significantly
lower FDP limits for the late evening and early morning hours. APA also
stated that the TNO Report has not been validated in the aviation
context, and that consequently, the FAA should proceed more cautiously
in increasing the existing limits for augmented operations.
    Table C differentiates between different FDP departure times
because of the type of rest that flightcrew members receive prior to
beginning the FDP. As discussed in more detail below, section 117.25
requires a 10-hour rest period with a minimum 8-hour sleep opportunity
immediately before a flightcrew member begins his or her FDP. Based on
this requirement, flightcrew members who begin an FDP in the morning
will obtain their pre-FDP sleep at night during the WOCL. Conversely,
flightcrew members who begin an FDP later in the day or at night will
obtain their pre-FDP sleep during the daytime. Because sleep taken at
night during the WOCL is more restful than sleep taken during the
day,\63\ flightcrew members who begin their FDP in the morning will be
better rested than flightcrew members who begin their FDP later in the
day or at night. Accordingly, Table C sets higher FDP limits for
augmented FDPs that begin in the morning and lower FDP limits for
augmented FDPs that begin later in the day or at night.
---------------------------------------------------------------------------

    \63\ See, e.g., James K. Wyatt, et al., Circadian temperature
and melatonin rhythms, sleep, and neurobehavioral function in humans
living on a 20-h day, Am. J. Physiol. 277 (4), at R1160-62 (1999);
Torbjorn Akerstedt & Mats Gillberg, The Circadian Variation of
Experimentally Displaced Sleep, Sleep, Vol. 4, No. 2, at 159-69
(1981).
---------------------------------------------------------------------------

    In selecting the specific timeframes for Table C, the FAA was
primarily concerned with the quality of pre-FDP rest obtained by the
flightcrew members, and not with whether those flightcrew members' FDP
required them to work during the WOCL. This is because the redundancy
inherent in an augmented operation ensures that there are extra
flightcrew member(s) available to take over the duties of someone who
becomes unduly fatigued during the WOCL. Since the timeframes of the
unaugmented FDP limits in Table B were calibrated to ensure that
unaugmented flightcrew members with long FDPs do not work during the
WOCL, the specific timeframes of the augmented FDP limits in Table C
(which address a different concern) are different from the timeframes
of Table B.
    The FAA has considered Drs. Belenky and Graeber's suggestion that,
based on unpublished modeling data studying long-haul flights, there is
no need to differentiate between the different departure times so long
as in-flight rest was provided during the second half of the flight.
The FAA notes that the modeling data cited by Drs. Belenky and Graeber
relies on in-flight rest being provided during the second half of the
flight. However, in order to provide operational flexibility to air
carriers, this rule requires that only the pilot who will be flying the
aircraft during landing receive his or her in-flight rest during the
second half of the FDP. As such, the FAA is unpersuaded by the fatigue
modeling data cited by Drs. Belenky and Graeber because that data does
not take into account the fatigue levels of all the members of the
augmented flightcrew.
    The FAA has also considered ATA's argument that augmented flights
leaving later in the day would provide in-flight sleep during the WOCL
for flightcrew members who would be manipulating the controls during
landing. However, there is little real-world data concerning the extent
of the mitigation provided by in-flight sleep during the WOCL. The FAA
is particularly concerned about whether the benefits of in-flight WOCL
sleep would outweigh the less-restful daytime sleep obtained by
flightcrew members who begin FDPs later in the day. Consequently, the
FAA has decided to retain the shorter FDP limits for augmented FDPs
that begin later in the day, but this position may change if FRMS-
provided real-world data addresses the FAA's concerns in this area.
    The FAA has decided to retain the departure-time-based approach in
Table C because, as discussed above, that approach is necessary to take
into account the quality of rest that a flightcrew member receives
immediately prior to beginning an FDP. However, in response to industry
concerns, the FAA has determined that a slight upward adjustment to the
FDP limits in Table C would not have an adverse effect on safety. This
is because, as discussed in the Flight Time section, the flight-time
limits for augmented operations effectively limit the time that each
augmented flightcrew member spends flying an aircraft to approximately
8.5 hours. Accordingly, the FAA has increased each of the FDP limits in
Table C by one hour. The FAA is also open to the possibility of further
increasing the FDP limits in Table C if additional data is provided, as
part of the FRMS process, showing that longer augmented FDPs do not
have an adverse impact on safety.
    The FAA has considered the labor groups' concern that the specific
limits in Table C somewhat deviate from the TNO Report's rationale.
However, the FAA believes that these deviations are justified in light
of the fact that the flight-time limits in this rule curtail the time
that flightcrew members spend engaged in the fatiguing activity of
piloting an aircraft. As discussed above, each of the augmented flight-
time limits has been calibrated so that each flightcrew member only
spends approximately 8.5 hours flying the aircraft. Because the
remainder of each flightcrew member's FDP is spent either resting or
doing less-fatiguing activities, the FAA has determined that an upward
deviation from the TNO Report is justified in this case.
    The FAA agrees that the TNO Report has not yet been validated in
the aviation context. However, the TNO

Report contains the latest scientific evaluation of onboard rest
facilities, and the report also contains the most comprehensive
evaluation of these facilities. Consequently, the FAA finds the TNO
Report to be persuasive in this case.
    The FAA understands the need to proceed cautiously with setting the
limits for augmented operations. That is why this rule largely retains
the existing flight-time limits for augmented flights. These flight-
time limits curtail the time-on-task of each flightcrew member and
serve as a crucial mitigation measure against fatigue. The specific
flight-time limits are set at levels with which the FAA has significant
operational experience and that have scientifically been shown to be
relatively safe.\64\ As discussed above, given the time-on-task
mitigation provided by the flight-time limits, the FAA has determined
that a slight increase to the proposed FDP limits would have no adverse
impact on flight safety.
---------------------------------------------------------------------------

    \64\ See Folkard, supra note 15, at 98 (showing an exponential
increase in accident risk after the 8th and 9th hour of work).
---------------------------------------------------------------------------

    NACA stated that the proposed language was unclear as to whether
the two-hour in-flight rest opportunity was required for each augmented
flight segment. Drs. Belenky and Graeber criticized the proposed
requirement that flightcrew members manipulating the controls during
landing receive their in-flight rest during the last flight segment.
They stated that the last flight segment on an augmented flight may be
short, in which case the flightcrew members manipulating controls
during landing would not receive their in-flight sleep during the most
optimal FDP time. As an alternative, Drs. Belenky and Graeber suggested
allowing in-flight rest to occur before the last flight segment, but
then limiting the flightcrew members to only conducting one more
landing after their in-flight rest. ATA and CAA endorsed Drs. Belenky
and Graeber's analysis.
    ATA, CAA, Atlas Air, Delta, and UPS criticized the proposed
requirement that in-flight rest for flightcrew members manipulating the
controls occur during the last flight segment. ATA stated that to
accommodate this requirement, the last flight segment would have to be
at least 3.5 hours long, which would not accommodate some current
operations. ATA and UPS added that turbulence or other factors
affecting the final leg--such as a diversion--may also prevent the
landing pilot from receiving a full two hours' rest on the last leg.
UPS stated that a customer in a supplemental operation may require a
short final segment. Atlas Air stated that some of its customers
request short flight segments as the last segments of an FDP.
    ATA and Delta recommended that the in-flight rest for flightcrew
members landing the aircraft be permitted to take place during the last
six hours of the FDP. UPS recommended that the required in-flight rest
for the landing flightcrew take place during the last eight hours of
the FDP.
    NACA recommended doing away with the two-hour and ninety-minute in-
flight rest requirements altogether, arguing that shorter amounts of
rest were also recuperative. In support, NACA cited a NASA study
showing that a short in-cockpit nap mitigated short-term fatigue. NACA
also stated that NTSB records do not reveal a single accident involving
an augmented crew in which fatigue was a factor.
    Drs. Belenky and Graeber also argued that the 2-hour required in-
flight rest opportunity could be broken up and distributed over
multiple flight segments. In support, they cited the 2003 Bonnet and
Arand clinical review for the proposition that rest of less than 2
hours would be beneficial in the augmentation context. They also cited
a NASA study showing that short cockpit naps could be used to mitigate
short-term fatigue.
    ALPA, IPA, CAPA, Flight Time ARC, and other labor groups suggested
that the 2-hour sleep requirement for the flightcrew member
manipulating the controls during landing apply to both flightcrew
members who will be occupying a control seat during landing. These
commenters emphasized that both flightcrew members manipulate the
controls, i.e., the non-flying pilot normally operates flaps, landing
gear and radios and performs monitoring so he must be equally alert.
The commenters added that there are also other high workload
circumstances where both pilots are manipulating the controls such as
when a landing must be rejected or decision-making is required for
diversion. Conversely, Delta stated that only one flightcrew member
actually manipulates the controls to land an aircraft while the other
flightcrew member at the control station performs secondary functions.
    NJASAP asked whether the 2-hour and 90-minute rest requirements for
augmented operations were cumulative. Specifically, NJASAP asked
whether flightcrew members who will be manipulating the controls during
landing are required to have in-flight rest totaling 3.5 hours. NJASAP
and North American Airlines also asked whether there was a minimum
length for a flight segment in an augmented FDP. NJASAP suggested that
each flight segment in an augmented FDP should be long enough for a
flightcrew member to gain sufficient amounts of in-flight rest. North
American Airlines suggested that subsections 117.19(c) and (d) be
eliminated in order to prevent confusion. NJASAP also asked when the
flightcrew member who will land the plane should end his or her in-
flight nap and take his or her space at the flight controls.
    The reason that the proposed rule required two hours of rest during
the last flight segment for flightcrew members who will be manipulating
the aircraft controls during landing was to ensure that the landing
flightcrew members obtain fatigue-mitigating rest close to the time
that they begin the landing. However, the FAA agrees with commenters
that requiring the rest to take place during the last flight segment
unnecessarily limits existing operations, some of which use a short
flight segment as the last segment of an augmented operation. As such,
this section has been amended to require that the flightcrew member who
will be flying the aircraft during landing receive his or her in-flight
rest during the second half of the FDP. This amendment allows air
carriers flexibility with scheduling flight segments for augmented FDPs
while at the same time ensuring that the landing flightcrew member
receives at least two hours of continuous rest close to the time that
he or she will be landing the aircraft.
    The FAA has also considered the NASA study cited by NACA. This NASA
study showed that a 40-minute sleep opportunity resulting in a 20-26
minute nap created a relative improvement in alertness for the 90-
minute period following the nap. However, this study does not justify
eliminating the requirement that the flightcrew member who will be
flying the aircraft during landing receive two hours of rest during the
second half of the FDP. This is because the NASA study did not
establish whether the 20-26 minute nap mitigated fatigue for more than
90 minutes after the nap was taken. As such, if a landing flightcrew
member takes his or her in-flight rest at the beginning of the FDP, it
is unclear from the results of the NASA study whether the benefits from
the short in-flight nap would still exist at the end of that flightcrew
member's FDP when that flightcrew member is engaged in the safety and
work-intensive task of landing an aircraft.
    The FAA also notes that it is retaining the requirement that the 2
hours of rest be continuous. This is because there is an overhead cost
associated with getting

to sleep, and a person waking up from a nap also does not immediately
become fully alert upon waking up. Consequently, if a person takes only
one continuous nap, the going-to-sleep/waking-up costs only have to be
paid once. However, if a single nap is split up into multiple naps,
those costs have to be paid each time a nap is taken. Because augmented
flights will only be in the air for a limited amount of time, the
additional going-to-sleep/waking-up costs would reduce the total amount
of time available for recuperative in-flight rest. As such, to maximize
the amount of recuperative rest obtained by augmented flightcrew
members and minimize the costs associated with going to sleep and
waking up, the minimum in-flight rest requirements in this section
require that the rest be continuous.
    As Delta pointed out, only one flightcrew member actually flies the
aircraft during landing while the other flightcrew member on the flight
deck performs secondary functions. While these secondary functions are
important, they are not as task-intensive as landing an airplane.
Therefore, this section only requires two hours of in-flight rest in
the second half of the FDP for the pilot who will be flying the
aircraft during landing. The regulatory language in this section has
been clarified accordingly. The regulatory language in this section has
also been amended to clarify that the ninety-consecutive-minute rest
opportunity is only necessary for the pilot who will be performing the
secondary monitoring duties on the flight deck during landing.
    In addition, the 2-hour and 90-minute rest requirements for
augmented operations are not cumulative. If a flightcrew member only
performs secondary monitoring duties during landing, that flightcrew
member is only required to have a minimum of 90-minutes of in-flight
rest. If a flightcrew member flies an aircraft during landing, that
flightcrew member is required to have a minimum of 2 hours of in-flight
rest in the second half of his or her FDP.
    Based on these rest requirements, at least one flight segment in
the second half of the augmented FDP of a flightcrew member who will be
flying an aircraft during landing must exceed two hours so that the
flightcrew member can obtain his or her minimum continuous in-flight
rest. This flight segment need not be the last flight segment of the
FDP. The two hours of in-flight rest simply needs to take place in the
second half of the FDP of the flightcrew member who will be flying the
aircraft during landing.
    The flightcrew member who will be flying the aircraft during
landing should end his or her in-flight nap and assume control of his
or her duty station before the top of the descent, which is about 45
minutes to 1 hour before landing. This is will allow the flightcrew
member to take into account all of the surrounding circumstances before
reducing the aircraft's altitude in preparation for an eventual
landing.
    NJASAP asked whether certificate holders could use augmentation on
domestic operations. ATA asked that the FAA ``affirmatively state in
the rule text that for the purposes of operational reliability and
flexibility, carriers can augment any flight that would not otherwise
require and/or qualify for augmentation.'' A number of air carriers
stated that augmentation on domestic flights should be permitted
because the science underlying domestic and international augmentation
is the same.
    Conversely, three individual commenters, APA, NJASAP, and Captain
Sullenberger stated that augmented flightcrews should be used only on
international and not domestic flights. NJASAP emphasized that
``[a]ugmented crews were intended to allow an aircraft to fly to a
destination which was too far to reach under the flight rules governing
two flightcrew members, meaning a flight route too long over a
geographical region which prohibited the allowing of changing crews.''
APA stated that domestic flights are capable of replacing the crew
between flight segments, and thus, they do not have the same need for
augmentation as international flights.
    This rule permits augmentation on domestic and international FDPs
that meet the criteria set out in section 117.17. This is because, as
the air carriers correctly pointed out, augmentation mitigates fatigue
the same way on both domestic and international flights. Therefore,
augmentation allows air carriers to safely schedule longer FDPs both
domestically and internationally.
    While augmentation was originally designed to allow air carriers to
schedule longer flights, that is not a sufficient justification to
limit augmentation to international flights. As an initial matter, some
domestic flights are longer than some international flights. Thus, for
example, a flight from Atlanta to Mexico City, which is an
international flight, is shorter than a flight from Washington DC to
Los Angeles, which is a domestic flight. In addition, augmentation
provides safety benefits on shorter flights as well as longer flights.
A flightcrew member working on an 8-hour augmented FDP will be able to
obtain in-flight rest and all of the other benefits of augmentation.
Consequently, the augmented flightcrew member will have a less-
fatiguing FDP than an unaugmented flightcrew member working on a
similar FDP.
    The FAA has determined that the ability to replace flightcrew
members between flight segments is also not a sufficient justification
for prohibiting augmentation on domestic flights. Many of the air
carriers that fly international routes have a substantial international
presence and could easily replace flightcrew members between flight
segments on international flights. Conversely, some air carriers do not
have a substantial presence at some of the smaller domestic airports,
and these air carriers may find it more difficult to replace flightcrew
members between domestic flight segments involving those airports.
    Because augmentation provides the same amount of fatigue mitigation
on both domestic and international flights and because there is no
meaningful justification for prohibiting augmentation on domestic
flights, this rule permits augmentation on both domestic and
international flights.
    NACA, CAA, North American Airlines, and Capital Cargo objected to
augmented flights being limited to three flight segments. Capital Cargo
stated that multi-segment augmented FDPs are safe because flightcrew
members on those FDPs receive in-flight rest. Conversely, ALPA, IPA,
CAPA, NJASAP, Flight Time ARC, and other labor groups stated that the
TNO report was only intended for one-segment flights, and as such,
multi-leg augmentation should only be allowed when no crew change is
possible. ALPA emphasized that ``[m]ulti-leg augmentation should never
be allowed solely for the purpose of extending a flight duty period.''
NJASAP asserted that multi-leg domestic augmentation is counter to the
intent behind augmentation. IPA, CAPA, and IBT Local 1224 suggested
that only two flight segments should be permissible for an augmented
FDP.
    As discussed in the Unaugmented FDP section, there is evidence that
additional flight segments increase flightcrew member fatigue. Because
existing augmented operations generally do not exceed three flight
segments, the FAA has little data concerning the effects of FDPs
consisting of more than three flight segments on the fatigue levels of
augmented flightcrew members. As such, the FAA has decided to permit
augmented FDPs of three flight segments or less, which are used in
existing operations, and to require

additional FRMS-provided data from air carriers wishing to exceed the
three-flight-segment limit.
    ATA and UPS stated that the FDP limits for four-pilot crews are
counter to science because they permit longer FDPs for pilots who land
during the WOCL than for pilots who do not land during the WOCL. As
such, ATA suggested that the limits for four-pilot operations ``be
adjusted to uniformly reflect the maximum values currently set forth in
the table.'' ATA stated that such an adjustment would make this rule
similar to other standards like CAP-371.
    Conversely, IPA, CAPA, IBT Local 1224, and Flight Time ARC
suggested that the FAA not allow four-pilot augmentation for flights
with a Class 3 rest facility. These commenters argued that a Class 3
rest facility only provides marginal rest, and placing more pilots on
board with this type of facility would just increase the likelihood
that there will be more fatigued pilots.
    As discussed above, the specific timeframes in Table C were
calibrated to take into account only the quality of rest received by
each flightcrew member before beginning an FDP. Because of the
redundancy safeguards inherent in augmentation, the FAA determined that
there was less of a safety concern associated with augmented pilots
flying an aircraft during the WOCL.
    Turning to the distinction between three- and four-pilot
flightcrews, the reason that Table C sets lower limits for three-pilot
crews than it does for four-pilot crews is that, in a three-pilot crew,
each pilot spends more time piloting the aircraft. Take, for example, a
12-hour flight segment. Because two pilots are required to operate the
aircraft, pilots in a four-pilot crew working in shifts of two would
each spend 6 hours on the flight deck. Conversely, pilots in a three-
pilot crew working in shifts of two would each spend 8 hours on the
flight deck. Because pilots working as part of a three-pilot crew spend
more time piloting the aircraft and less time resting, Table C sets
lower FDP limits for three-pilot crews.
    The FAA understands that this distinction makes this rule different
from other regulatory rules, such as CAP-371, which do not distinguish
between three and four-pilot augmented crews. Here, while CAP-371 does
not distinguish between three- and four-pilot crews, it addresses the
safety issues associated with augmentation flights in other ways by
requiring three hours of in-flight rest during augmented operations
\65\ instead of the ninety minutes to two hours required by this rule.
---------------------------------------------------------------------------

    \65\ CAP-371, section 15.3.
---------------------------------------------------------------------------

    The FAA has also decided to retain augmentation for four-pilot
flightcrews on flights with a Class 3 rest facility because, even
though these flights have a lower-quality rest facility, each of the
pilots in the four-pilot flightcrew will spend less time piloting the
aircraft than the pilots in a three-pilot flightcrew. Consequently, the
members of the four-pilot augmented flightcrew will accumulate less
fatigue during their flight than the members of the three-pilot
augmented flightcrew. The lower quality of the Class 3 rest facility is
instead reflected in the relatively-low FDP limits associated with that
facility.
    APA suggested amending subsection 117.19(e) to add a requirement
that the PIC-type-rated flightcrew member be fully qualified and
landing current. APA stated that the flightcrew member(s) flying the
aircraft need to be capable of performing a landing because unforeseen
circumstances during the flight may require the flightcrew member(s) in
the cockpit to make a prompt emergency landing. NJASAP stated that all
flightcrew members in an augmented operation should be type-rated.
    In response to APA's concern, the language in section 117.19(e) has
been amended to require that at least one flightcrew member on the
flight deck must be qualified in accordance with 14 CFR
121.543(b)(3)(i). A flightcrew member qualified in accordance with
section 121.543(b)(3)(i) will be both fully qualified and landing
current.
    Turning to NJASAP's concern about all flightcrew members being
type-rated, the FAA notes that the existing regulations require the
second in command (SIC) to be type-rated for all non-domestic flights.
See 14 CFR 61.55(a)(3). While these regulations do not require the SIC
to be type-rated on domestic flights, the FAA has determined that 14
CFR 121.543(b)(3)(i) requires a high degree of training, and having at
least one flightcrew member on the flight deck who is qualified in
accordance with this section provides sufficient staffing to safely
operate the aircraft and respond to any unforeseen circumstances that
may arise.
    Boeing asked for clarification about whether FDPs consisting of a
mix of augmented and unaugmented flights are subject to Table B or
Table C.
    The FDP and flight-time limits for augmented operations were set at
higher levels based on the assumption that flightcrew members working
on those operations would obtain the fatigue-mitigation benefits of
augmentation. A flightcrew member who works on an unaugmented flight
does not obtain these fatigue-mitigation benefits. As such, if an FDP
contains both an augmented and an unaugmented flight, that FDP is
subject to the unaugmented FDP-limits set out in Table B and the
unaugmented flight-time limits set out in Table A.
    IPA, CAPA, Flight Time ARC, and other labor groups also suggested
that, to ensure proper in-flight rest, this rule require a Class I rest
facility for any augmented FDP in which the flight time exceeds 12
hours.
    As discussed in the Flight Time section, the flight-time limits for
augmented FDPs have been set so that each flightcrew member flies the
aircraft for approximately 8.5 hours. Because this flight-time
restriction limits each flightcrew member's time-on-task to acceptable
levels, there is no need to impose minimum rest facility limitations
for sub-categories of augmented operations.
    NACA suggested, without elaboration, that the FDP limits for
unacclimated flightcrew members be decreased by 1 hour instead of the
proposed 30 minutes. ALPA, IPA, IBT Local 1224, and Flight Time ARC
argued that the proposed 30-minute reduction for unacclimated
flightcrew members is too simplistic. As an alternative, these
commenters proposed a Table D, containing FDP limits for unacclimated
flightcrew members, which decreased unacclimated flightcrew member FDP
times by values ranging from 20 to 50 minutes (depending on the time of
day).
    The 30-minute FDP-limit reduction for unacclimated flightcrew
members was imposed to account for the additional fatigue experienced
by these flightcrew members. The FAA is unaware of NACA's reasons for
suggesting that the FDP reduction for unacclimated flightcrew members
be increased to one hour.
    Turning to the suggestions put forward by the labor groups, because
the unacclimation reductions set out in the commenters' suggested Table
D are relatively close to the FAA-proposed 30-minute reduction, the FAA
has decided to retain the 30-minute reduction for the sake of
regulatory simplicity. As commenters have pointed out elsewhere, parts
of this rule are somewhat complex, and as such, the FAA has determined
that adding another table solely for unacclimated flightcrew members
would add undue complexity to this section.
    ALPA, IPA, CAPA, and IBT Local 1224 recommended changing the label
in Table C for ``Time of start'' to clarify that the timeframes
specified in Table C are based on home base or acclimated

time. The FAA adopts this recommendation, and the label in Table C has
been changed to clarify that the ``Time of start'' in Table C is based
on home base or acclimated time.

I. Schedule Reliability

    In the NPRM, the FAA proposed reporting requirements to facilitate
realistic scheduling by the certificate holders. Proposed Sec.  117.9,
Schedule reliability, would have required the certificate holder to
adjust (1) its system-wide FDPs if the total actual FDPs exceed the
scheduled FDPs more than 5% of the time; and (2) a specific FDP if it
is shown to exceed the schedule 20% of the time. The certificate holder
would have to adjust its schedule within 60 days for any FDP(s) that
exceeded the above-stated percentages.
    The FAA also proposed that each certificate holder must submit a
report every two months detailing the adjustments described above (the
overall schedule reliability and pairing-specific reliability) and
include the following information: (1) The carrier's entire crew
pairing schedule for the previous two-month period, including the total
anticipated length of each set of crew pairings and the regulatory
limit on such pairings; (2) the actual length of each set of crew
pairing; and (3) the percentage of discrepancy between the two data
sets on both a cumulative, and pairing-specific basis.
    No commenters supported the requirements for schedule reliability
as proposed. Many commenters argued that the proposed requirements were
unnecessary as they would not do anything to mitigate transient,
cumulative or chronic fatigue. Others believe that the proposal was
seriously flawed and that adjustments to the proposed requirements were
necessary.
    Pinnacle, RAA, ATA, Alaska Airlines, Continental, American Airlines
and Capital Cargo International Airlines (CCIA) contend that the
schedule reliability section should be deleted entirely. They argue
that these proposed requirements do not advance fatigue mitigation and
present unjustified costs and burdens on certificate holders. RAA
stated that the NPRM did not set forth any discussion of a statistical
basis/reality check for the selection of a 5% FDP ``late arrival'' rate
for the certificate holder's operation as a whole, or as the trigger
point for when the certificated holder must take action to ``adjust.''
Similarly, RAA states that there is no discussion to support the
selection of 20% for a particular FDP that actually exceeds the
scheduled time. RAA also commented that there is limited likelihood
that the flightcrew member FDP reliability analysis under the NPRM
would differ greatly from an airline's on-time arrival statistics even
if the proposed regulatory text is changed to reflect a 14-minute
``grace period'' that DOT affords in its on-time reporting statistics.
    Several commenters, including CAA, UPS, World Airways, American
Eagle Airlines (AE), and ALPA, also objected to the schedule
reliability provision and suggested that instead of reporting when
actual FDPs exceed scheduled FDPs, certificate holders should only
report FDPs that exceed the maximum limits under the regulations. They
argue that as long as the flightcrew member's FDP falls within the
parameters of the maximum permitted under the regulation, the
certificate holder must have the operational flexibility to manage
schedules as they determine. The commenters also stated that a
reporting schedule which requires a certificate holder to detail
occurrences that exceed the maximum limits provided in Tables B and C,
and to adjust the schedules that consistently exceed those limits, is
reasonable.
    Commenters also submitted varying timeframes for the reporting.
Some recommended 30 days, other suggested quarterly reporting. There
were various comments on how long the certificate holder had before
taking corrective action.
    IBT Local 1224, IPA, the Flight Time ARC, and FedEx ALPA
recommended that the schedule reliability section extend to flight
segments as well.
    IATA commented that any reporting requirements should relate
directly to fatigue and not to compliance with published schedules. UPS
stated that the reporting requirements should be seasonal to comport
with schedule changes. UPS also argued that schedule reliability would
actually increase fatigue because certificate holders would pad time
spent on the ground during multi-segment FDPs, which would result in a
corresponding reduction in restorative layover rest. UPS and NAC
contend that this section addresses domestic scheduled operations and
is illogical for others, particularly non-scheduled operators.
    The FAA acknowledged in its Response to Clarifying Questions that
the NPRM discussion on schedule reliability was confusing. The FAA also
acknowledges that this section as proposed raised considerable concerns
from virtually all commenters. After reviewing the comments, the FAA
concludes that the concept of schedule reliability is better addressed
by the simpler approach recommended by the group of commenters, who
suggested reporting actual FDPs that exceed the maximum regulatory
limits. This is discussed in detail in the next section.

J. Extensions of Flight Duty Periods

    The FAA agrees that FDPs that exceed the maximum FDP permitted
under Table B are the ones that directly impact fatigue and must be
addressed by the certificate holder. Adopting this approach will make
the certificate holder accountable for scheduling FDPs realistically.
While a certificate holder can schedule FDPs up to the maximum
presented in the tables, it is unlikely to do so because of the
cumulative limits (weekly and monthly) on FDPs. This approach addresses
a significant portion of the commenters' concerns. Proposed section
117.9 is deleted and the FAA adopts new Sec.  117.19 Flight Duty Period
Extensions.
    This new section sets forth the limits on the number of FDPs that
may be extended; implements reporting requirements for affected FDPs;
and distinguishes extended FDPs due to unforeseen operational
circumstances that occur prior to takeoff from those unforeseen
operational circumstances that arise after takeoff. For purposes of
maintaining all requirements for FDP extensions in a single section,
the provisions permitting extended FDPs based on unforeseen
circumstances proposed in Sec.  117.15 FDP: Un-augmented operations and
Sec.  117.19 FDPs: Augmented flightcrew are now codified in Sec.
117.19.
    RAA, Southwest Airlines and World Airways object to the pilot in
command being the decision maker on whether to extend an FDP.
Continental, however, recommends that the decision to extend a FDP
should be a joint decision between the pilot in command and the
certificate holder. APA commented that the decision of the pilot in
command is crucial in determining whether to extend an FDP.
    The FAA agrees that the responsibility for determining whether a
FDP needs to be extended rests jointly with the pilot in command and
the certificate holder. This ensures that one party is not taking
excessive action over another party, and that proper considerations are
factored into the decision-making. Paragraph (a)(1) of this section
permits, under unforeseen operational circumstances that arise prior to
takeoff, the pilot in command and the certificate holder to extend the
maximum FDP permitted in Table B and C by two hours.
    In the NPRM, the FAA specifically questioned whether the proposed
two-hour extension was appropriate.

SWAPA opposed any extension beyond the free 30-minute extension and
argued that this would invite abuse. NJASAP supported one extension up
to two hours, as long as compensatory rest was applied following the
extension. IPA supported the two-hour extension as reasonable but
opposed the three-hour extension for augmented operations because
greater rest opportunities are not provided for those operations. APA
supports the limits on extensions and argues in particular that the 12-
13 hour period repeatedly has been cited as a point at which accident
risk increased dramatically. APA also commented, however, that there
are certain circumstances in which a FDP can be safely extended beyond
the two hours contemplated in the NPRM. NACA supports a two-hour
extension for both augmented and unaugmented operations.
    The FAA agrees that an extension must be based on exceeding the
maximum FDP permitted in Table B and C. It is unreasonable to limit
extensions on FDPs that are less than what the certificate holder can
legally schedule. In addition, there is a 30-minute buffer attached to
each FDP to provide certificate holders with the flexibility to deal
with delays that are minimal. However, after the 30-minute buffer, any
time that the FDP needs to be extended, the requirements and
limitations of this section apply. In the NPRM, the FAA proposed a two-
hour FDP extension for unaugmented operations due to unforeseen
operational circumstances and a three-hour FDP extension for augmented
operations under similar situations. The FAA concludes that there is no
distinction for FDP extension based on whether the operation is
conducted by an augmented flightcrew. The difference between
unaugmented and augmented operations is accounted for by the different
hourly limits in Tables B and C. The hourly limits of Table C were
developed in consideration of the extra flightcrew members and rest
facilities onboard the aircraft for augmented operations that mitigate
the effects of longer FDPs. There is no further mitigation that
warrants an additional hour for an augmented crew. The FAA believes
that two hours is reasonable and provides the certificate holder with
sufficient operational flexibility to adjust for unforeseen operational
circumstances. If an unforeseen operational circumstance occurs prior
to takeoff, a flightcrew member cannot accept an extended FDP if the
completion of that FDP would be more than two hours beyond the maximum
FDP permitted under Table B and C for that flight.
    In the NPRM, the FAA proposed that an extension of an FDP of more
than 30 minutes may occur only once in any 168 consecutive hour period.
Hawaiian Airlines, IPA, IBT Local 24, Alaska Airlines, Aloha Air Cargo
and several individual commenters supported this proposal. One
commenter suggested one extension in a 90-day period. SkyWest, United,
FedEx Express, ATA, and CAA argue that one extension is too restrictive
and does not allow any operational flexibility to recover a schedule
after an event. SkyWest suggested up to three extensions per week with
a total of eight per month. ATA argued that the once in 168 hours rule
``is another example of a requirement made unnecessary by other
mitigations in the NPRM and which will result in unjustified adverse
impacts.'' ATA and CAA support the statements submitted from Drs.
Belenky and Graeber, who commented ``that clear science supports that
extended work hours over consecutive work days reduces the opportunity
for sleep, which can lead to cumulative sleep loss and fatigue.
However, there is no scientific evidence to support limiting an
extension to once in seven days.'' They further comment that extensions
should not be permitted on consecutive days in order to allow for sleep
recovery and no more than two extensions within any one 168 hour
period. RAA, Continental, North American, Southwest and two individuals
requested two extensions in a 168 consecutive hour period. Kalitta Air
and North American Airlines support two non-consecutive extensions in
168 hours, with a 16-hour rest period required if the second extension
actually occurs.
    Lynden Air Cargo, Southern Air and NACA object to the limit on
extensions. They argue that supplemental, non-scheduled operations
require flexibility to schedule their operations that is not needed by
the domestic scheduled community because they have crews on reserve for
use in lieu of extensions.
    The FAA is not persuaded by the commenters that more than one
extension is appropriate within a 168 consecutive hour period with one
exception, discussed below. The elements of the flight and duty
requirements adopted in this rule present a conceptual departure from
the practice that is in place under the current rules. Under the
current rules, extensions of flight time were largely unrestricted as
long as a flightcrew member was provided with compensatory rest. Under
the requirements adopted today, rest is prospective and the certificate
holders are responsible to schedule realistically so that FDP limits
can be maintained. Permitting weekly extensions simply encourages
scheduling to those extensions and undercuts the purposes of strict
limits on FDPs.
    In response to the commenters however, the FAA is modifying one
aspect of this requirement. In the NPRM, an FDP extension was limited
to once every 168 consecutive hour period. While this limited potential
abuse of extensions, it did result in an illogical outcome based on
certain facts. For example, a flightcrew member that has an FDP
extended on Day 1 and then has two days off would be unable to accept
another extended FDP on Day 4. After having 48 hours rest, that
flightcrew member would not be subject to fatigue based on a two-hour
extended FDP. Paragraph (a)(2) provides that an extension of the FDP of
30 minutes or more may occur only once prior to receiving a rest period
described in Sec.  117.25(b).\66\ This provides certificate holders
with one extended FDP but resets the clock for the 168 consecutive
hours limit if a rest period of 30 hours or more has been received.
Furthermore, the FAA is mindful of the daily tracking and
recordkeeping/compliance burden placed on both individual flightcrew
members and the certificate holders by a rolling 168 consecutive hour
period. This modification will alleviate this tracking requirement.
---------------------------------------------------------------------------

    \66\ Section 117.25(b) provides that before beginning any
reserve or FDP, a flightcrew member must be given at least 30
consecutive hours free from all duty in any 168 consecutive hour
period, subject to certain limitations.
---------------------------------------------------------------------------

    The FAA has included, in paragraph (a)(3), that a flightcrew
member's FDP may not be extended due to unforeseen operational
circumstances that occur prior to takeoff if such extension could cause
the flightcrew member to exceed the cumulative FDP limits specified in
Sec.  117.23(c). The basis for this provision is that prior to takeoff
a flightcrew member will know whether the delay will result in the
flightcrew member exceeding the cumulative limits. If so, the
flightcrew member cannot continue the flight.
    In lieu of the reporting requirements proposed under the schedule
reliability, the FAA adopts a two-prong requirement for reporting
extended FDPs. In addressing unforeseen operational circumstances, it
is critical to distinguish those situations that arise prior to takeoff
and those that arise after takeoff. Under both situations, the
certificate holder must report to the FAA within 10 days any FDP that

exceeded the maximum FDP permitted by Table B or C by more than 30
minutes. In this report, the certificate holder must describe the FDP
and the circumstances surrounding the need for an extension. If the
situation giving rise to the extension occurred prior to takeoff, the
certificate holder must address in this report whether the
circumstances giving rise to the extension were within its control.
Since it is prior to takeoff, once the certificate holder becomes aware
of such issue, the certificate holder and pilot-in-command have
discretion to evaluate the situation and determine whether it is
permissible and appropriate to extend the applicable FDPs and continue
with the flight or whether it is more appropriate to replace the
affected flightcrew member. Therefore, in situations where the
circumstances were within the certificate holder's control, the
certificate holder must include in its report the corrective actions
that it intends to take to minimize the need for future extensions. The
certificate holder then has 30 days to implement such corrective
actions. For situations that are not within the certificate holder's
control, it is unlikely that there is a corrective action that can be
taken. Therefore, under these scenarios, the certificate holder must
simply report the extension within 10 days and provide the details
surrounding the need for the extended FDP.
    Similarly for situations that arise after takeoff, the certificate
holder and pilot in command have very little discretion concerning FDPs
and flight time limits. Therefore, if an FDP or flight time needs to be
extended due to unforeseen circumstances that occur after takeoff, the
pilot-in-command and the certificate holder may extend the subject FDPs
and flight time, to the extent necessary to safely land the aircraft at
the next destination airport or alternate airport, if appropriate. In
addition, the extended portion of the flightcrew member's FDP and
flight time will be permitted in the flightcrew member's weekly and
annual cumulative limits on FDP and flight time limitations. The
certificate holder also must report the extension to the Administrator
within 10 days of occurrence with the same level of detail as described
above.
    The reports for extended FDPs and flight time will be forwarded to
the appropriate certificate-holding district office where the FAA will
monitor all extensions filed. The FAA will review the circumstances
surrounding the need for the extensions and if appropriate, whether the
circumstances were, in fact, beyond the certificate holder's control.
As explained in the NPRM, this determination is on a case-by-case
basis. Certificate holders must be aware of scheduling operations into
and out of chronically delayed airports. Similarly, certificate holders
must be mindful of anticipated weather conditions, e.g., predicted snow
storms/blizzards affecting certain airports in the winter. Obviously,
not all weather occurrences, ATC delays, or a variety of other
situations can be anticipated and addressed by the certificate holder.
However, situations that result from inadequate planning are within the
certificate holder's control and will warrant corrective action.
    The FAA believes that the above requirements will result in
realistic scheduling of FDPs. The FAA selected 10 days for the time
period to file a report because it is within the time period for
retrieval of ATC and weather data in the event that data is necessary
for an investigation. This information may be necessary in addressing
extended FDPs so it is critical that the FAA receive the report within
the same timeframe. In addition, when situations occur that require an
extension, the certificate holder must look at the offending segment
and identify whether adjustments are needed.
    It must be noted that the FAA will investigate each filed report
denoting an extended FDP and flight time. This investigation would be
conducted by the certificate management office responsible for day-to-
day oversight of the air carrier. If the circumstances are found to be
within the certificate holder's control, the certificate holder has
responsibility to determine the corrective action and to implement that
corrective action within the time period required under the
regulations. Failure to adhere to the adopted requirements may result
in enforcement by the FAA.

K. Split Duty

    Sleep studies show that sleep which takes place during the day is
less restful than sleep that takes place at night.\67\ Other studies
indicate that working during the WOCL substantially degrades the
ability of a flightcrew member to safely perform his or her duties.\68\
One of the problems that this rule was intended to address is the
performance degradation experienced by flightcrew members who conduct
overnight FDPs and perform their duties during the WOCL after receiving
less-restful daytime sleep. This rule addresses this problem by
incentivizing fatigue mitigation measures.
---------------------------------------------------------------------------

    \67\ See, e.g., Wyatt, supra note 64, at R1160-62; Akerstedt,
supra note 64 at 159-69.
    \68\ See NASA, supra note 22, at 19-34.
---------------------------------------------------------------------------

    One of these fatigue mitigation measures is split duty which is
based on the premise that there are times during an unaugmented
nighttime FDP when a certificate holder could reasonably provide a
flightcrew member with an opportunity for rest. This rest opportunity
(opportunity to sleep) would allow a flightcrew member to get some
sleep during the night. The nighttime sleep could be used to mitigate
the performance degradation created by working through the WOCL.
    To incentivize split duty rest, the FAA proposed that a flightcrew
member who received a split duty rest opportunity be allowed to extend
his or her FDP by 50% of the available split duty rest opportunity.
Under the FAA's proposal, the split duty rest opportunity had to be at
least 4 hours long, and it could not be used to extend an FDP beyond 12
hours. The rest opportunity had to be calculated from the time that the
flightcrew member actually reached the suitable accommodation (sleep
facility).
    NJASAP opposed the proposed split duty extension, but noted that
the proposed rule presented an improvement over existing limitations on
such operations. NJASAP argued that split duty sleep is a theoretical
concept that may result in cumulative fatigue and circadian disruption.
In support of its argument, NJASAP cited to a study showing that pilots
who obtained 7 hours of sleep at night scored consistently worse than
pilots who obtained 9 hours of sleep at night. Given this study and the
theoretical nature of split duty, NJASAP cautioned the FAA against
awarding an FDP extension based on split duty rest.
    Conversely, ATA stated that ``science and operational experience
supports the concept that a flightcrew member can recuperate because of
the opportunity to sleep during a period of their FDP.'' CAA strongly
supported the recognition of split duty as a fatigue mitigation
measure. One individual commenter also supported the extension of FDPs
through split duty schedules.
    NJASAP also asked whether the four-hour threshold was mandatory or
whether split duty credit could be obtained for split duty rest that
was less than four hours. ATA and UPS argued that the four-hour split
duty threshold is arbitrary and not science-based. ATA also criticized
as unscientific the NPRM's assumption that there is increased overhead
involved with falling asleep during a split duty rest. Conversely,
FedEx ALPA supported the four-hour split duty threshold, stating

that the four-hour threshold is a valid conservative approach until
more scientific data is collected.
    Drs. Belenky and Graeber cited a 2003 Bonnet and Arand clinical
review for the proposition that ``any sleep longer than 20 minutes
provides full minute-by-minute recuperative value.'' Based on this
review, Drs. Belenky and Graeber asserted that, for night operations,
``any time behind the door of more than 30 minutes would have
recuperative value.'' As such, Drs. Belenky and Graeber argued that the
four-hour split duty threshold is not supported by science. ATA, CAA,
and FedEx supported this conclusion.
    NACA, Kalitta Air, Atlas Air, and NAA cited a NASA study, which
states that a 45-minute cockpit nap, including use of a jump seat, with
a 20-minute recovery resulted in increased alertness for a minimum of
90 minutes of the flight. These commenters argued that, if this type of
benefit could be achieved through a cockpit nap, it could definitely be
achieved through a ground rest facility.
    The FAA agrees with ATA and CAA that split duty is a valid fatigue
mitigation measure. Science has shown that naps can serve to mitigate
fatigue.\69\ Consequently, split duty naps taken at night will permit a
flightcrew member to obtain restful nighttime sleep in the middle of
his or her FDP. This restful nighttime sleep will decrease that
flightcrew member's fatigue level, and will allow him or her to safely
work for a longer period of time. As such, the FAA has retained the
split duty FDP extension in this rule.
---------------------------------------------------------------------------

    \69\ See Daniel J. Mollicone, et al., Optimizing sleep/wake
schedules in space: Sleep during chronic nocturnal sleep restriction
with and without diurnal naps, Acta Astronautica 60, at 354-61
(2007) (examining the fatigue mitigation potential of naps taken
during the day).
---------------------------------------------------------------------------

    In response to comments about specific split duty provisions, the
FAA conducted further SAFTE/FAST modeling to examine the safety-
relevant effects of changing the provisions of the split duty section.
The SAFTE/FAST model works by predicting flightcrew member
effectiveness on a 0 to 100 scale for each minute of that flightcrew
member's FDP. Lower predicted flightcrew member effectiveness results
in a lower SAFTE/FAST number. An effectiveness level of 77 is
approximately equivalent to the effectiveness of someone with a blood
alcohol concentration of 0.05.
    With regard to the 4-hour threshold, that threshold was included in
the proposal to ensure that all flightcrew members obtain a minimum
amount of restful sleep during split duty. Upon further modeling, the
SAFTE/FAST model showed that a split duty break of less than 3 hours
with the corresponding FDP extension would, over a 5-night period,
result in flightcrew member effectiveness dropping below 77 for a
portion of the FDP. Conversely, a split duty break of at least 3 hours
resulted in flightcrew member effectiveness consistently staying above
77 over a 5-night period. Accordingly, this section has been amended to
reduce the threshold for the split duty extension to a 3-hour split
duty break. In response to NJASAP's question, split duty rest that is
less than 3 hours simply counts as part of a flightcrew member's FDP
and does not serve to extend the maximum FDP limits.
    The FAA disagrees with Drs. Belenky and Graeber's assessment of the
Bonnet and Arand clinical review. The studies examined in this clinical
review tested the impact that sleep fragmentation had on restfulness
and the potential resultant daytime sleepiness. During the course of
the studies, subjects would be allowed to fall asleep, and their sleep
would then be intermittently disrupted. The studies found that if one's
sleep is interrupted every 20 minutes following sleep onset during the
night (when one is normally sleeping), that person's daytime
sleepiness, as measured by the Mean Sleep Latency Test (MSLT), is the
same as someone who has not had their sleep interrupted.
    There are two problems with applying the Bonnet and Arand clinical
review to split duty. The first problem is that the MSLT results
measured by the studies analyzed in the clinical review do not
necessarily mean that the performance capabilities of subjects who had
their sleep interrupted at 20-minute intervals were equivalent to
subjects who did not have their sleep interrupted. All the MSLT results
mean is that, when MSLT measurements were taken of subjects who had
their sleep interrupted, these subjects did not fall asleep within the
MSLT's protocol termination at 20 minutes.
    The second problem with applying these studies to split duty sleep
is that split duty sleep does not involve sleep fragmentation, but
rather a restriction on the total amount of sleep provided during the
night. A flightcrew member engaging in split duty sleep will presumably
not have his or her sleep cycle intermittently disrupted. Instead, that
flightcrew member's total split duty sleep amount may be significantly
lower than the 8-hour minimum necessary to recover from fatigue.
Because the Bonnet and Arand clinical review did not analyze any
studies that actually examined the ``recuperative value'' of receiving
less than 8 hours of sleep, that review is not applicable to the
minimum threshold necessary to ensure a sufficient amount of split duty
sleep.\70\
---------------------------------------------------------------------------

    \70\ In a previous Bonnet article, the author also states that
``* * * [i]t does appear that any repetitive stimulation of
sufficient magnitude to precipitate any changes in ongoing EEG is
sufficient to make sleep nonrestorative.'' Bonnet MH. Sleep
restoration as a function of periodic awakening, movement, or
electroencephalographic change. Sleep, Vol. 10, at 371 (1987).
---------------------------------------------------------------------------

    As the commenters correctly pointed out, a NASA study showed that a
40-minute sleep opportunity resulting in a 20-26 minute nap created a
relative improvement in alertness for the 90-minute period following
the nap. However, there are three problems with using this study to
justify extending a night FDP. First, the NASA study was conducted to
see if alertness might be maintained or improved long enough to more
safely complete a scheduled flight. The NASA study was not conducted to
determine the conditions necessary to extend the flight duty period.
Second, the study did not establish whether the 20-26 minute nap
mitigated fatigue for more than 90 minutes after the nap was taken.
    The third problem with using the above study to extend an FDP is
that this study did not explore the full extent of the fatigue
mitigation created by the 20-26 minute nap. For example, if a 20-minute
split-duty nap was to be used to extend an FDP so that it infringes
deeper into the WOCL, would the 20-minute rest provide sufficient
mitigation to counter the extra fatigue created by the additional
infringement on the WOCL? Because the study concerning the 20-26 minute
nap did not provide an answer to the issues discussed above, the FAA
has declined to utilize it in determining the threshold rest amount for
the split duty FDP extension.
    NJASAP asked whether the split duty rest must be scheduled in
advance or whether it could be adjusted as necessary by the certificate
holder. ATA stated that the 4-hour threshold is operationally unsound
because split duty periods are ``calculated dynamically in real time,
based upon the actual amount of rest opportunity afforded.'' ATA
provided an example of ``split duty rest periods [that] may occur
during breaks at a hub while cargo is loaded on an aircraft.'' In those
cases, ``[c]rewmembers [would] receive rest in ground facilities during
the aircraft loading process.'' UPS disagreed with the extension being
based on the flightcrew member's actual rest time ``behind the door''
because it removes an air carrier's ability to shorten split

duty rest in response to an unforeseen circumstance, such as a weather
event. UPS stated that this is a significant change from current
practice because, currently, split duty rest most often occurs during
an unforeseen circumstance. To adjust for this change, UPS asserted
that air carriers would have to delay outbound flights, which will
increase pilot fatigue by delaying the onset of post-FDP rest.
    The FAA has amended the split duty section to clarify that split
duty rest must be scheduled in advance, and that the actual split duty
rest break may not be less than the scheduled split duty break. The
reason for the advance scheduling requirement is that section 117.5(b)
requires flightcrew members to determine at the beginning of their FDP
whether they are sufficiently rested to safely perform the assigned
FDP. In order to accurately perform this assessment at the beginning of
their FDP, flightcrew members need to know approximately when their FDP
is going to end. Thus, flightcrew members must be notified of any
planned split duty extensions before they begin their split duty FDP so
that they can accurately self-assess, at the beginning of the FDP,
whether they are capable of safely performing their duties throughout
the entire FDP. Thus, for example, a flightcrew member who feels fit to
accept an overnight FDP that contains five hours of split duty sleep
may not feel fit to accept an overnight FDP that contains only three
hours of split duty sleep.
    In addition, knowing in advance about split duty rest allows a
flightcrew member to prepare for, and to maximize, the rest
opportunity. For example, a flightcrew member who does not know whether
he or she will have a split duty break may drink a cup of coffee only
to subsequently find out that he or she must take a three-hour split
duty rest 20 minutes later. In contrast, a flightcrew member who knows
in advance when he or she is taking a split duty break will not drink
coffee shortly before the break. Because flightcrew members must
determine their fitness for duty before beginning an FDP and because
they must conduct themselves in a way that maximizes their rest
opportunities, they must be informed prior to commencing an FDP, about
the full extent of the split duty rest that they will receive during
the FDP.
    The FAA understands that this departs from the current air carrier
practice of reducing split duty rest in order to recover a schedule
during unforeseen circumstances. To mitigate the impact of this change
and account for unforeseen circumstances, this rule provides air
carriers with a two-hour FDP extension (discussed previously) that they
can use to recover their schedules if unforeseen circumstances arise.
    NJASAP asked whether an air carrier could obtain the split duty
credit if its flightcrew members do not actually occupy the suitable
accommodation during the split duty rest opportunity. UPS criticized
the split duty regulation as not taking into account the actual amount
of sleep that a pilot receives.
    Split duty rest taken under this section does not begin to count
until the flightcrew member reaches the suitable accommodation. If the
flightcrew member never reaches the suitable accommodation, then that
flightcrew member's split duty break will not qualify for a longer FDP.
The FAA also emphasizes that, as discussed above, section 117.5(a)
requires a flightcrew member to report for duty rested. By virtue of
that requirement, flightcrew members must take advantage of any rest
periods that are provided, and use them for their intended purpose,
which is to sleep.
    The FAA has considered UPS' suggestion of amending the split duty
extension to track the actual amount of sleep that a flightcrew member
receives instead of the length of the split duty break. However, this
type of standard would be very difficult to implement because air
carriers would need to track when each flightcrew member actually falls
asleep. Because this would place a substantial burden on air carriers,
the FAA ultimately decided to give credit for the length of the split
duty rest opportunity instead of the amount of actual sleep received by
the flightcrew members.
    Drs. Belenky and Graeber asserted that the 50% split-duty credit
was unreasonably conservative for split-duty rest that is taken during
usual bedtime hours. However, Drs. Belenky and Graeber cautioned that
the 50% credit ``may be warranted for split duties that require daytime
sleep.'' ATA stated that the 50% credit was unjustified because a sleep
opportunity longer than 20 minutes provides a full minute-by-minute
recuperative value. ATA criticized the NPRM's underlying assumption
that a four-hour sleep opportunity would only result in two hours of
sleep, arguing that this assumption did not apply to ground-based
suitable accommodations.
    Northern Air Cargo asked for a more generous split duty credit. ATA
proposed a split duty credit that increases in proportion to the length
of the split duty rest. CAA and FedEx proposed a split duty credit
ranging from 100 to 300%, based on the time of day in which the credit
is given.
    As stated above, in response to comments, the FAA conducted further
SAFTE/FAST modeling to determine whether the split duty provision could
be modified without decreasing safety. The modeling has revealed that a
100% credit for split duty rest would not result in flightcrew member
effectiveness dropping below 77 for any portion of a series of 5-night
FDPs. As such, the split duty credit has been increased to provide for
an extension equal to 100% of the split duty rest. The FAA has
considered CAA and FedEx's suggestion of providing more than a 100%
credit, but, due to the concerns associated with nighttime flying, the
FAA would need additional data to provide more than a 100% credit for
split duty.
    The FAA was also concerned with the fact that the above comments
appear to show some misunderstanding of how the split duty section
works. In order to clarify the meaning of the split duty section, the
FAA has amended this section as follows.
    First, the split duty framework, as set out in the NPRM, would
count split duty rest as part of a flightcrew member's FDP, and then
extend that FDP by the amount of the split duty credit. Now that the
split duty credit has been increased to 100%, the FAA has determined
that the NPRM's split duty framework is needlessly complicated. As
such, this section has been amended so that split duty rest that meets
the requirements of this section will simply not count as part of the
FDP.
    Second, split duty rest was intended to be taken at night so that
it could provide flightcrew members with restful nighttime sleep. See
75 FR 55866. To ensure that the split duty rest credit is not awarded
for rest taken during the day, this section has been amended to require
that split duty rest only be taken between 22:00 and 05:00 local time.
    Third, as the name implies, ``split duty'' rest should be provided
in the middle of a flightcrew member's FDP. To ensure that split duty
rest is not taken earlier, the FAA has added a condition that split
duty rest cannot be provided before the completion of the first flight
segment in an FDP. Finally, the FAA has moved all of the split duty
conditions into subsections to improve their readability. These changes
should provide additional clarity, and ensure that the split duty
section is used in the intended manner.
    UPS, Kalitta Air, and ATA stated that the credit given for split
duty rest in ground-based suitable accommodations was less than the
credit given for some

augmented flights, which provide a lower quality rest in aircraft-based
rest facilities. UPS pointed out that, under the proposed rule, ``[a]
90-minute rest opportunity for a relief officer on an augmented flight
in an aircraft with a Class I rest facility permits five additional
hours of operation versus an un-augmented flight.'' UPS added that this
disparity between augmented flights and split duty ``is even more
illogical given that at a ground facility, all flightcrew members
receive the same sleep opportunity, whereas while on board, only one
pilot can sleep at a time.'' NACA proposed a split duty credit that is
consistent with the credit given for Class 1, 2, and 3 rest facilities
in augmented FDPs.
    Augmented flights and split duty provide different amounts of
credit because they pose different safety risks. An augmented flight
contains more than the minimum number of flightcrew members, which
allows the flightcrew members to work in shifts during a flight to
safely fly the aircraft. If, during the flight, a flightcrew member
realizes that he or she is too tired to safely perform his or her
duties, the extra flightcrew member(s) can simply take over those
duties and safely land the flight at its intended destination.
    Split duty, on the other hand, applies only to unaugmented flights,
which contain the minimum number of flightcrew members necessary to
safely fly an aircraft. If, during an unaugmented flight, a flightcrew
member realizes that he or she is too tired to safely perform his or
her duties, there is no one there who could take over those duties.
Instead, the fatigued flightcrew member must eventually land the
aircraft to the best of his or her ability. Because a fatigued
flightcrew member on an unaugmented flight presents a far greater
safety risk than a fatigued augmented flightcrew member, the FAA used a
more conservative approach in determining the split duty credit than it
did in determining the limits for augmented operations. However, the
FAA is open to the possibility of awarding greater credit for split
duty within the scope of an FRMS if a certificate holder is able to
provide data that shows that additional credit would not reduce safety.
    ATA suggested that the FAA allow split duty FDPs to extend beyond
the proposed limit on split duty extensions in order to consistently
apply the principles that underlie augmented operations. RAA criticized
the 12-hour split-duty FDP limit as arbitrary, arguing that it
unnecessarily limits FDPs that contain a large amount of restful split
duty sleep. RAA also pointed out that the 12-hour limit permits greater
split duty extensions for less-safe overnight flights that have a
shorter FDP limit. RAA proposed abolishing the limit on split duty
extensions. SkyWest proposed setting the split duty FDP limit at 14
hours if the split duty rest is at least 4 hours long. CAA and FedEx
stated that the split duty FDP limit should be set at 15 hours.
    The SAFTE/FAST modeling that was conducted in response to comments
shows that there are no safety concerns with increasing the split duty
limit to 14 hours. This section has been amended accordingly. However,
the FAA has reservations about a split duty limit that exceeds 14
hours. This is because section 117.25 now requires a 10-hour rest
period, and if an FDP is longer than 14 hours, a flightcrew member's
FDP/rest cycle will exceed 24 hours. This type of cycle, if done
consecutively, will result in the beginning of a flightcrew member's
FDP being pushed back each day by the number of hours that the previous
day's FDP/rest cycle exceeded 24.
    As an example, take an FDP that begins at 5 p.m. That FDP is
normally 12 hours long, but with a 7-hour split duty break, that FDP
would end at noon. The flightcrew member must then obtain 10 hours of
rest, which means that he or she would start the next day's FDP at 10
p.m. The 10 p.m. FDP is normally 11 hours, but with 6 hours of split
duty rest, it would end at 3 p.m. the next day. The flightcrew member
would then receive 10 hours of rest, which would result in his or her
next FDP starting at 1 a.m. Thus, with no limit on split duty FDPs, a
flightcrew member could, in three days, go from a 5 p.m. to a 10 p.m.
to a 1 a.m. FDP start time. This type of shifting of FDP start times
could have serious adverse effects on cumulative fatigue, and without
more data, the FAA has determined not to take the risk of allowing
split duty FDPs to exceed 14 hours.
    NACA, Atlas Air, and NAA stated that, because section 117.5 gives a
flightcrew member the discretion to terminate an FDP, there is no need
to further restate the flightcrew prerogative to accept or decline
split duty accommodations or FDP extensions here.
    The FAA agrees with the above commenters, and this section has been
amended accordingly. The FAA once again emphasizes that, as discussed
above, section 117.5(a) requires a flightcrew member to report for duty
rested. By virtue of that requirement, flightcrew members must use
their rest periods for the intended purpose which is to obtain sleep.

L. Consecutive Nights

    As discussed above, one type of fatigue that this rule addresses is
cumulative fatigue. In formulating this rule, the FAA was particularly
concerned about cumulative fatigue caused by repeatedly flying at
night. See 75 FR 55867. SAFTE/FAST modeling showed substantially
deteriorating performance after the third consecutive nighttime FDP for
flightcrew members who worked nightshifts during the WOCL and obtained
sleep during the day. Id. However, the FAA noted that if a sleep
opportunity is provided during each nighttime FDP, that sleep
opportunity may sustain flightcrew member performance for five
consecutive nights.
    To account for the above factors, the FAA proposed to limit
nighttime FDPs to three consecutive nights. However, the FAA proposal
allowed a flightcrew member to exceed the three-night limit if that
flightcrew member received at least four hours of split duty rest
during each of his or her nighttime FDPs.
    ATA, NACA, AAC, five individual commenters, and a number of air
carriers objected to the consecutive-night limit, arguing that it was
unreasonable and ignored operational experience. ATA stated that
``[t]he industry's substantial experience with nighttime operations
shows that pilots who frequently perform night duty are well suited to
consecutive night duties because they have training and experience
specific to such operations.'' NACA, NAA, and Kalitta Air suggested
completely removing the consecutive-night limit, arguing that
restricted nighttime FDP limits made the consecutive-night limit
redundant. AAC also suggested removing the consecutive nighttime limit,
arguing that some pilots are capable of adjusting their circadian
rhythm to effectively sleep during the day. AAC asserted that a three-
consecutive-night limit would unfairly penalize those pilots.
    Conversely, one individual commenter stated that consecutive
nighttime operations lower alertness. NJASAP, IPA, and IBT Local 1224
supported the consecutive-nights limit. IPA and IBT Local 1224
indicated that, according to science and operational experience, a
flight duty period encompassing the hours of 0200 and 0600 is
challenging, as fatigue is more likely. These commenters stated that
the additional fatigue is a result of working during the WOCL and
having the rest period occur during the daytime.
    Nighttime operations are particularly fatiguing because flightcrew
members who work during these operations do so

during the WOCL after obtaining less-restful daytime sleep. Studies
have shown that this type of work not only leads to transient fatigue,
but also leads to cumulative fatigue if repeated over a series of
consecutive nights.\71\ SAFTE/FAST modeling also shows flightcrew
member effectiveness decreasing after a flightcrew member works on
consecutive nighttime FDPs. In addition, a study conducted by the
Federal Motor Carrier Safety Administration (FMCSA) found in a
laboratory setting that working five nights in a row while sleeping
during the day leads to impaired continued performance even if a 34-
hour ``restart'' rest period is provided at the conclusion of the five-
night work period.\72\ This study indicates that simply relying on the
required 30 hour rest period in a rolling 168 hour (one week) period is
insufficient to assure sustained performance for individuals working
nighttime FDPs.
---------------------------------------------------------------------------

    \71\ See Philippa H. Gander, et al., Flight Crew Fatigue IV:
Overnight Cargo Operations, Aviation, Space, and Environmental
Medicine, Vol. 69, No. 9, Sec. II (Sep. 1998) (discussing sleep debt
that builds up over successive nighttime work shifts); Philippa H.
Gander, et al., Crew Factors in Flight Operations VII:
Psychophysiological Responses to Overnight Cargo Operations, NASA
Technical Memorandum 110380 (Feb. 1996) (discussing the impact of
night shifts on flightcrew members).
    \72\ See Hans P.A. Van Dongen, Gregory Belenky, Investigation
Into Motor Carrier Practices to Achieve Optimal Commercial Motor
Vehicle Driver Performance, Report No: FMCSA-RRR-10-005.
---------------------------------------------------------------------------

    In order to address cumulative fatigue caused by consecutive
nighttime FDPs, the FAA has decided to retain the consecutive-night
limitation. This limitation is necessary because the restricted
nighttime FDP limits in Table B only address the transient fatigue
caused by working at night. The limits in Table B remain the same
regardless of how many consecutive nighttime FDPs a flightcrew member
works, and as such, they do not address the cumulative fatigue caused
by repeatedly working through the nighttime hours. With regard to AAC's
suggestion that some flightcrew members can effectively sleep during
the day, this suggestion (which may be true for certain individuals)
generally goes against scientific evidence showing that working on
consecutive nighttime FDPs creates a sleep debt.\73\ Since regulations
are drafted to address the majority of the population, the FAA believes
the approach adopted here is appropriate.
---------------------------------------------------------------------------

    \73\ Id.
---------------------------------------------------------------------------

    Drs. Belenky and Graeber cited the Mollicone 2007 and 2008
laboratory studies for the proposition that a sleep period that was
split into two naps (one at night and one during the day) had the same
effect as a single continuous block of sleep taken at night. Drs.
Belenky and Graeber suggested that 2 hours of split duty rest ``should
sustain performance across more than three consecutive nights'' as long
as flightcrew members obtained at least 5 hours of sleep during the
day. ATA, CAA, and UPS endorsed Drs. Belenky and Graeber's analysis and
recommendation.
    RAA, ATA, UPS, FedEx and a number of other air carriers added that
requiring a 4-hour split duty break in order to exceed 3 consecutive
nights would result in more first-night shifts and more day and night
duty schedule switches because air carriers will schedule pilots for
multiple 3-night series of FDPs rather than a single 5-night FDP
series. SkyWest stated that a consecutive-night restriction may disrupt
its continuous duty operations, which operate at night and provide
flightcrew members with a 4-6 hour rest opportunity. UPS emphasized
that the proposed consecutive-night restriction would significantly
disrupt its existing business operations. Atlas Air added that cargo
air carriers cannot reasonably provide a 4-hour mid-duty break under
their current business models.
    ATA and CAA emphasized that the consecutive-night limit would
disproportionately impact the cargo industry because that industry
relies heavily on night operations. UPS stated that, during a night
shift, its ``flightcrew members typically enjoy, on average, at least a
two hour rest in [its] state of the art sleep facilities.'' FedEx
stated that its flightcrew members are typically provided mid-duty rest
ranging from 2 to 4.5 hours while freight is offloaded, sorted, and
reloaded. UPS asked the FAA to recognize the recuperative value of mid-
duty sleep that exceeds 20 minutes.
    The Mollicone studies cited by Drs. Belenky and Graeber have, at
best, only a limited applicability to the consecutive-night limit
because the subjects in those studies received a large block of anchor
sleep at night and mid-duty rest breaks during the daytime. In
contrast, flightcrew members working on night shifts receive their
large block of anchor sleep during the daytime, which, as other studies
have shown, provides them with sleep that is less restorative than
nighttime sleep.\74\
---------------------------------------------------------------------------

    \74\ See Wyatt, supra note 64; Akerstedt, supra note 64.
---------------------------------------------------------------------------

    The FAA was concerned, however, with comments indicating that the
4-hour-mid-duty rest threshold for exceeding the 3-consecutive-night
limit was operationally unworkable. The FAA notes that, even though
all-cargo operations are not required to abide by part 117, those all-
cargo operations that opt into part 117 would be subject to the
consecutive-night limit. In response to concerns raised by the
commenters, the FAA conducted further SAFTE/FAST modeling to examine
the safety ramifications of changing the length of the mid-duty rest
break necessary to exceed the 3-consecutive-night limit. The SAFTE/FAST
modeling showed that a 5-night FDP, in which a flightcrew member was
provided with a 2-hour mid-duty rest break each night, was actually
safer than a 3-night FDP with no rest break. The modeling also showed
that breaks of less than 2 hours were insufficient to account for the
cumulative fatigue of working on multiple consecutive nights.
    In response to the data provided by the SAFTE/FAST modeling, the
FAA has amended the consecutive-night limit to allow a flightcrew
member to work for up to 5 consecutive nights if he or she receives a
2-hour mid-duty rest break each night. This amendment will greatly
reduce the burden of the consecutive-night limit on cargo industry that
opts into this rule because FedEx and UPS' comments indicate that these
carriers already provide their crewmembers who work nightshifts with an
average of 2 hours of mid-duty rest. This will allow continuous duty
operations to be conducted 5 nights a week if these operations provide
flightcrew members with at least 2 hours of mid-duty rest.
    RAA, Kalitta Air, Kalitta Charters, Capital Cargo, and four
individual commenters suggested amending the consecutive-night limit to
permit four nights without any mid-duty rest breaks. ALPA, IPA, SWAPA,
IBT Local 1224, and Flight Time ARC suggested allowing four consecutive
nighttime FDPs if there is a 12-hour rest period after each FDP. UPS
suggested that, if the FAA restricts consecutive nighttime operations,
unaugmented flightcrews should be allowed to operate at Table C FDP
limits so long as they have received a sleep opportunity in a rule-
compliant ground-based facility.
    This rule does not allow 4 consecutive nighttime FDPs without a
mid-duty rest break because flightcrew member performance deteriorates
after a third consecutive nighttime FDP. Increasing the length of the
rest between FDP periods is not the preferred way of resolving the
issue because nightshift workers get their between-FDP rest during the
daytime. Because daytime sleep is less restful than nighttime sleep,
the FAA has chosen to focus its regulatory efforts on nighttime mid-
duty rest breaks instead of longer daytime

rest breaks. However, if air carriers provide the FAA with FRMS data
showing that longer daytime breaks can sufficiently mitigate cumulative
fatigue, the FAA may allow those air carriers to exceed the
consecutive-night limit. In addition, as discussed in the preceding
section, the FAA has reduced to 2 hours the mid-duty-break threshold
necessary to work during 5 consecutive nights. This reduction will
greatly reduce the burden of the consecutive-night limit on air
carriers.
    The FAA also declines UPS' proposal of allowing an unaugmented
flightcrew working a nightshift to work at the FDP levels specified in
Table C. As discussed above, the augmented FDP limits in Table C are
higher than the unaugmented FDP limits in Table B because augmentation
provides a number of fatigue-mitigation benefits. In contrast, the
consecutive-night limit is simply intended to account for the
cumulative fatigue caused by working at night and does not replicate
the benefits provided by augmentation. Accordingly, imposition of the
consecutive-night limit is not sufficient to allow unaugmented
flightcrews to work on the longer FDPs that are permitted for augmented
flightcrews.
    A number of commenters asked the FAA to define ``nighttime FDP.''
Many of the commenters suggested that ``nighttime FDP'' be defined as
an FDP that infringes on the WOCL. The consecutive-night limit is
intended to apply to FDPs that infringe on the WOCL because operations
conducted during the WOCL significantly increase cumulative fatigue.
Consistent with the commenters' suggestion, the consecutive-nighttime-
operations section has been amended to clarify that the consecutive-
night limit only applies to FDPs that infringe on the WOCL. In
addition, in light of the amendments that have been made to the split-
duty section, the consecutive-nighttime-operations section has also
been amended to clarify that an FDP whose split-duty rest infringes on
the WOCL counts as a nighttime FDP for the purposes of this section.
    NJASAP asked the FAA for clarification about how the rule
determines whether two nighttime FDPs are ``consecutive.'' Consecutive
nights are determined based on calendar nights. Thus, if a flightcrew
member works on a WOCL-infringing FDP during one night, and then works
during a WOCL-infringing FDP during the following night, that
flightcrew member will have worked on two consecutive nights. If,
however, the flightcrew member works one night, has the next night off,
and then works the following night, these nighttime FDPs would not be
considered ``consecutive'' for the purposes of this section.
    ATA also objected to applying the consecutive-night limit to
augmented operations. It stated that augmented flightcrew members
receive significant inflight rest, and that the consecutive-night limit
was redundant as applied to augmented FDPs.
    Rest on the ground in a suitable accommodation is superior to rest
onboard an aircraft while that aircraft is in flight. As such, any
augmented operations that span more than three consecutive nights must
mitigate the fatigue of these operations by providing flightcrew
members with the two hours of mid-duty rest in a suitable accommodation
required by this section.
    ATA stated that, because simulator training is now considered part
of an FDP, the consecutive-night limit would also limit training
opportunities for flightcrew members. ATA argued that this is an
unnecessary burden because flightcrew members would receive a full rest
period after training.
    Simulator training is only considered to be part of an FDP if it
takes place before a flightcrew member flies an aircraft and there is
no intervening rest period taken pursuant to section 117.25. This is
because all duty after a legal rest and prior to flight is part of an
FDP. If the simulator training does not take place before a flightcrew
member flies an aircraft, the simulator training is not considered to
be part of an FDP, and it is unaffected by the consecutive-night limit.
    Two individual commenters asked the FAA to prohibit air carriers
from switching pilots from night to day shifts. These commenters also
asked that circadian rhythms not be shifted by more than two hours from
the prior day. However, these suggestions are outside the scope of this
rulemaking.

M. Reserve

    As stated in the NPRM, the term ``reserve'' has not been addressed
in the part 121 regulations; however this term has been the subject of
several legal interpretations which include a determination of when a
flightcrew member is on duty and whether the required rest associated
with a duty period is impeded by a flightcrew member being in a reserve
status. The FAA proposed that unless specifically designated otherwise,
all reserve is considered long-call reserve. Additionally, the time
that a flightcrew member spent on airport/stand-by reserve would be
part of that flightcrew member's FDP. For short-call reserve, the NPRM
proposed that all time spent within the reserve availability period is
duty; the reserve availability period may not exceed 14 hours; no
flightcrew member on short call reserve may accept and no certificate
holder may schedule the flightcrew member's next reserve availability
period unless that flightcrew member is given at least 14 hours rest;
and the maximum reserve duty period for an unaugmented operation is the
lesser of:

--16 hours, as measured from the beginning of the reserve availability
period;
--The assigned FDP, as measured from the start of the FDP;
--The FDP in Table B of this part plus 4 hours, as measured from the
beginning of the reserve availability period; or
--If all or a portion of a reserve flightcrew member's reserve
availability period falls between 0000 and 0600, the certificate holder
may increase the maximum reserve duty period by one-half of the length
of the time during the reserve availability period in which the
certificate holder did not contact the flightcrew member, not to exceed
3 hours.

    For an augmented operation, the NPRM proposed that the maximum FDP
is the lesser of the assigned FDP, as measured from the start of the
FDP; the FDP in Table C plus 4 hours, as measured from the beginning of
the reserve availability period; or if the reserve availability period
falls between a portion of 0000-0600, the maximum reserve availability
period may be increased by one-half the length of the time during which
the certificate holder did not contact the flightcrew member but capped
at 3 hours.
    The FAA proposed that long-call reserve does not count as duty and
that a flightcrew member would need to receive a 12-hour notice of
report time from the certificate holder if the flightcrew member is
being assigned an FDP that would begin before and operate into his or
her WOCL.
    Lastly, the NPRM proposed provisions that would permit a
certificate holder to shift a flightcrew member's reserve availability
period subject to meeting certain conditions.
    Commenters stated overall that the entire section was overly
complicated and complex, with some commenters stating that it also was
confusing and illogical. Industry largely objected to the
classification of short-call reserve as duty. ALPA, COPA, FedEx ALPA,
SWAPA and APA all commented favorably on short-call reserve as part of
duty. These comments were addressed

in the Definitions section, which removed short-call reserve from the
definition of the term ``duty.''
    NACA, Atlas, NAA, and Kalitta argue that limiting short call
reserve to 14 hours is unwarranted for their operations. Kalitta
separately recommended that the reserve availability period should be
16 hours followed by 8 hours off. Under Kalitta's recommendation, if a
flightcrew member on short-call reserve is called out within the first
six hours of that reserve availability period, he or she can utilize
the entire maximum FDP, as described in Table B or C. If the flightcrew
member is called out after the first six hours of the reserve
availability period, then all the time in short-call reserve should be
subtracted from the maximum FDP, unless the un-interrupted short-call
reserve included the flightcrew member's WOCL. Then the full period of
the WOCL should be considered rest. Kalitta argues that this will
permit long-haul, non-scheduled operators the ability to continue
current operations.
    NACA, Atlas, and NAA also argue the proposal is too restrictive
because the controlling limitation will always be the assigned FDP,
which is a maximum of 13 hours. UPS and ATA state that there is no
justification for limiting unaugmented short call reserve to assigned
FDP. They contend that this restriction materially deviates from the
ARC recommendation concerning this element of reserve.
    ATA further comments that using the FDP to set the maximum reserve
duty period directly contradicts the NPRM's definition of ``reserve
duty period'' as the reserve availability period plus the flight duty
period.
    RAA proposed instead that for unaugmented operations, if a
flightcrew member is given an FDP while on short-call reserve, the FDP,
measured from the time for reporting for assignment, is limited to the
Table B maximum FDP minus the full time spent on reserve during the
Reserve Availability Period (RAP) up to the report time. Northern Air
Cargo (NAC) contends that there is no logic in not allowing for the
full FDP after callout. Delta argued that while on reserve, limiting
reserve duty periods to scheduled FDP rather than maximum is overly
restrictive.
    ALPA, COPA, FedEx ALPA, SWAPA and APA submitted the chart below
depicting the maximum FDP permissible based on the start of time of the
reserve availability period:
[GRAPHIC] [TIFF OMITTED] TR04JA12.000

    They argue that the maximum reserve duty period, which would
include phone availability and/or FDP assignments, is measured from the
start of the RAP and ends at the earlier of the start of the RAP time
plus the value in Table E or the FDP in Table B. The purpose of this
process is to ensure that the reserve pilot does not have an allowable
FDP limit that is greater than the FDP of the line holder whom that
reserve flightcrew member is paired with and does not impact the
certificate holder because the line holder and reserve flightcrew
member end point will be the same.
    Peninsula Airways questions whether under this section, a
flightcrew member on short-call reserve must have had 14 hours of rest
period at the beginning of the current reserve availability period.
    The FAA agrees that the proposed reserve provisions were overly
complicated and has made numerous changes to reduce the complexity. The
ARC came to a number of conclusions during its discussion of reserve.
The FAA has decided to rely on the expertise represented in the ARC to
address the issue of reserve duty. The FAA does not support Kalitta's
proposal described above, which would increase the permissible reserve
availability period to 16 hours. Kalitta has not provided supporting
rationale that warrants modifying the collective opinion of the ARC.
Therefore, this rule adopts the proposal that limits the short-call
reserve availability period, in which the flightcrew member is not
called to report to work, to 14 hours.
    The FAA has modified the regulatory provisions addressing the
reserve duty period and unaugmented FDPs. Under the NPRM, the maximum
reserve duty period would be the lesser of 16 hours, the assigned FDP,
or the FDP under Table B plus four hours. The FAA agrees with the
commenters that limiting the reserve duty period to the assigned FDP
was overly restrictive and could result in situations where the reserve
duty period was unnecessarily short, and would be unworkable for the
certificate holders. The FAA has deleted that provision but retains the
other two proposed limitations for unaugmented operations. Therefore,
the adopted regulatory provisions addressing reserve and unaugmented
operations provide that the total number of hours a flightcrew member
may spend in a flight

duty period and reserve availability period may not exceed 16 hours or
the maximum applicable flight duty period in Table B plus four hours,
whichever is less. This will allow most FDPs to be accommodated by a
flightcrew member on short-call reserve. Additionally, the proposed
provisions for giving credit for not calling during the window of
circadian low are complicated and unnecessary given the above adopted
modifications. Therefore, the credit provisions have been dropped from
this rule.
    In response to the question posed by Peninsula Airways regarding
whether the flightcrew member, who has concluded a reserve availability
period, must have a 14 hour rest period before beginning the next
reserve availability period, the FAA modified this provision in
accordance with the amendments in Sec.  117.25 Rest period. A
flightcrew member must be given a 10 consecutive hour rest period
immediately before beginning the reserve or flight duty period. The
regulation governing reserve has been adjusted for consistency with the
rest provisions. Therefore, if a flightcrew member completes a reserve
availability period, he or she must receive a rest period, as required
in Sec.  117.25(e), prior to accepting a subsequent reserve
availability period.
    The FAA also does not agree with the comments from the labor
organizations that another Table is necessary for the short-call
reserve duty period. Those organizations argue that incorporating the
above chart would ensure that the reserve flightcrew member would not
have an allowable FDP that is greater than the line holder with whom he
or she is paired. This argument is not persuasive. Each flightcrew
member is subject to the maximum permissible FDP given that flightcrew
member's recent assignments and rest requirements. Consequently, it
isn't reasonable to artificially limit a reserve pilot to the FDP limit
of the line holding pilot when no such limit applies to the line
holding flightcrew members.
    Kalitta and UPS questioned why a flightcrew member on long-call
reserve and assigned an FDP that begins before and operates in the
WOCL, would require a 12-hour rest. These commenters argue that a line
holder may be scheduled for duty during the WOCL with 9 hours rest and
that the long-call reserve flightcrew member should have similar
treatment as the line holder.
    This provision simply requires that the affected flightcrew member
must receive 12 hours notice that he or she will be on duty during the
WOCL and will need to plan his or her rest during the day. This way,
the flightcrew member can structure the rest period in order to provide
the best sleep opportunity. As daytime rest is not as restorative as
nighttime rest, the flightcrew member may choose to take multiple naps
rather than attempting to get a full consecutive 8 hours of sleep
during the day. This is comparable to a lineholder who knows in advance
that he or she is scheduled for duty during the WOCL, and adjusts his
or her sleep opportunity accordingly.
    NJASAP questions why the rule does not limit long-call reserve. APA
also added that flightcrew members on long call reserve should receive
a rest period that includes a physiological night prior to assignment.
There is no reason to limit long-call reserve because, by definition,
the certificate holder must notify the flightcrew member prior to
receiving rest under 117.25(e). Similarly, as the flightcrew member is
receiving a 10 hour rest period prior to the flight, it is not
reasonable to limit that rest to only the hours between 0100 and 0700.
This would unnecessarily restrict the certificate holder's ability to
use long-call reserve.
    Kalitta and UPS oppose the provisions limiting the shifting of
reserve availability periods. RAA also opposes these provisions and
argues that they actually hinder fatigue reduction by forcing more
flightcrew schedule disruptions through delay or cancellations than
would otherwise be necessary. NACA, Atlas, and NAA contend that the
provisions addressing the shift of reserve availability periods are
unworkable because it restricts forward shifts to a maximum of 12
hours, which can ultimately result in stranded flights. These
commenters illustrate, as an example, if a flight is delayed for 13
hours, this rule would require the aircraft to sit on the ground for
hours because the reserve flightcrew would be unable to operate the
next flight until they have completed the required rest.
    The organizations representing labor also seek to limit, to once in
a rolling 168 hour period, the provision that would require a short
call reserve flightcrew member coming off of a 14 hour reserve
availability period to have a 14 hour rest before accepting an FDP that
begins before the flightcrew member's next reserve availability period.
The commenters contend that without this once per 168 hour limitation,
a flightcrew member could be in a cycle of continuous reserve
availability periods.
    Since the rest requirements mandate a rest period prior to
accepting any short-call reserve period and given the above
modifications to the rule, the FAA concludes that the limits on
shifting reserve availability periods are unnecessary and would have
added a level of complication that is not warranted. This provision is
not adopted.

N. Cumulative Limits

    In formulating this rule, the FAA found that ``[s]cientific studies
suggest that long periods of time on duty infringe upon an individual's
opportunity to sleep, thus causing a `sleep debt' which is also known
as cumulative fatigue.'' \75\ To limit the accumulation of cumulative
fatigue by flightcrew members, the FAA proposed a cumulative duty-
period limit of 65 hours in a 168-hour period (7 days) and a limit of
200 hours in a 672-hour period (28 days). These cumulative duty-period
limits were slightly increased for short-call reserve and for deadhead
transportation in a seat that allows for a flat or near flat sleeping
position.
---------------------------------------------------------------------------

    \75\ 75 FR 55871 and n.42 (citing scientific studies).
---------------------------------------------------------------------------

    The FAA also proposed cumulative FDP limits based on the standards
of other aviation authorities. The proposed cumulative FDP limits
restricted FDP to 60 hours in a 168-hour period and 190 hours in a 672-
hour period. In addition, the FAA proposed retaining the existing
cumulative flight-time limits, which are 100 hours in a 28-day period
and 1,000 hours in a 365-day period.
    Alaska Airlines stated that the proposed subsection 117.23(a)
concerning cumulative FDP limits was ambiguous and arguably made this
section apply to flights that a flightcrew member conducted on his or
her days off. Alaska Airlines and Delta argued that an air carrier
should not be held responsible for flights that a flightcrew member
performs on his or her days off that are not assigned by the air
carrier. Conversely, SWAPA stated that, due to the complexity of the
cumulative limits, the certificate holder should have the sole
responsibility of determining whether flightcrew members are in
compliance with the applicable cumulative limits.
    The cumulative limits in section 117.23 include any flying
performed by the flightcrew member on behalf of any certificate holder,
or 91K Program Manager during the applicable periods. It does not
include personal flying. Subsection 117.23(a) has been amended to
clarify this point. The reason that this section includes all flights
conducted for a certificate holder or program manager is because a
flightcrew member accumulates fatigue on those flights. A

flightcrew member accumulates fatigue whenever he or she flies an
aircraft. The flightcrew member does not accumulate less cumulative
fatigue simply because the flying is conducted for another operator.
    The FAA has considered the air carriers' argument that the proposed
subsection 117.23(a) may affect their scheduled flights as a result of
flights that they do not assign to their flightcrew members. However,
the FAA believes that its cumulative-limit approach is justified in
light of the fact that compliance with this rule is a joint obligation
that applies to flightcrew members as well as air carriers. Thus, the
FAA expects flightcrew members to inform their employing air carriers
of flying that they conduct on days off that would impact the
cumulative limits set out in this rule, thus allowing all parties to
abide by the applicable cumulative limits.
    The FAA also declines SWAPA's suggestion that air carriers bear
sole responsibility for determining compliance with the cumulative
limits. As discussed in the preceding paragraph, without flightcrew
member assistance, air carriers may not even know about some of the
flying performed by flightcrew members. While the rolling time periods
used in this section may not be as easy to keep track of as calendar
periods, the FAA expects both flightcrew members and air carriers to be
aware of how many hours the flightcrew members have worked and to abide
by the cumulative limits of this section.
    RAA opposed the cumulative duty-period limits, arguing that duty
was a nebulous concept that was hard to define, and that cumulative
duty-period limits are unnecessary in light of the cumulative FDP
limits. NACA and NAA stated that an air carrier should be able to
assign additional duty time if no further FDPs are contemplated because
``[t]here is no further risk of an aviation accident unless flight is
involved.'' NACA, UPS, and a number of other air carriers added that
the inclusion, in duty limitations, of administrative duties adversely
affected flight-qualified management personnel and addressed work-life
issues that had nothing to do with aviation safety. IPA disagreed,
arguing that ``[j]ust as the certificate holder tracks flight time and
flight duty periods, administrative duties should also be tracked.''
IPA stated that subordinate officials who work in an office all day and
fly at night are more likely to be fatigued.
    ATA and UPS stated that the proposed rule unfairly expands the
concept of duty to ``circumstances beyond the carriers' control such
as, random drug tests.'' RAA stated that the duty-period limits
essentially limited the time that flightcrew members spend on non-
flying tasks, but that this was not a significant factor in flightcrew
scheduling. These commenters added that air carriers could not always
control the types of seats available to deadheading flightcrew members,
and that they should not be penalized for being unable to provide
deadheading flightcrew members with flat or near flat seats.
    The FAA agrees with industry comments that cumulative duty-period
limits are unnecessary in this rule. Cumulative duty-period limits were
intended to address the following: (1) Deadheading, (2) short-call
reserve, and (3) air carrier directed non-flight activities that lead
to fatigue during flight. As discussed in other portions of this
preamble, the FAA has amended other parts of this rule to address
fatigue-related concerns raised by deadheading and short-call reserve.
    Turning to the fatigue-related issues of non-flight activities, on
reevaluation, the FAA has determined that the FDP limits in this rule
fully address the non-flight activities that could contribute to
flightcrew member fatigue. This is because the only non-flight
activities that have a significant impact on fatigue during flight are
activities that occur immediately before the flight without an
intervening rest period. Since there is no intervening rest between the
non-flight activities and piloting an aircraft, the fatigue accumulated
while performing these non-flight activities remains with the
flightcrew member when that flightcrew member pilots an aircraft.
Therefore, all non-flight activities that occur immediately before a
flight without an intervening rest period are part of an FDP and are
appropriately restricted by the FDP limits.
    The other non-flight (non-FDP) activities do not significantly
affect the fatigue experienced during flight because there is an
intervening rest period between these activities and the beginning of
an FDP. Consequently, the FAA has eliminated the cumulative duty period
limits from this rule.
    RAA, NACA, and a number of air carriers opposed the cumulative
flight-time limits, arguing that FDPs were the actual source of
flightcrew member fatigue. Because FDPs are limited by the proposed
cumulative FDP limits, these commenters argued that the cumulative
flight-time limits are unnecessary.
    Existing regulations impose 30-day flight-time limits of 100 hours
and calendar-year flight-time limits of 1,000 hours. The FAA has
administered these cumulative flight-time limits for over four decades,
and based on its operational experience, the FAA has found that
cumulative flight-time that falls within these limits is safe. Because
the FAA is unaware of any data showing that flight times exceeding
these limits are safe, the FAA has decided to retain cumulative
flightcrew member flight-time limitations within the existing limits.
    As the commenters correctly point out, because FDPs include flight
time, the FAA could have addressed the concern discussed in the
preceding paragraph by calibrating the cumulative FDP limits. However,
as discussed in the Flight Time Limits section of this preamble, the
FAA chose to retain the concept of flight-time limits in order to set
higher FDP limits and provide air carriers with more flexibility. If
the FAA eliminated the cumulative flight-time limits from this rule, it
would need to drastically reduce the cumulative FDP limits from the
limits that were proposed. This is because without cumulative flight-
time limits, the proposed cumulative FDP limits would allow flightcrew
members to accumulate flight time that significantly exceeds the
cumulative flight time permitted by existing regulations. To keep that
from happening and provide air carriers with more scheduling
flexibility, this rule largely retains the existing flight-time
cumulative limits and sets higher cumulative FDP limits than would
otherwise have been permissible.
    ATA, RAA, and a number of air carriers stated that imposing
cumulative limits for three different regulatory concepts (FDP, duty,
and flight time) was unjustified and overly burdensome. ATA stated that