An airliner is a large fixed-wing aircraft with the primary function of transporting paying passengers. Such aircraft are usually operated by an airline which owns or leases the aircraft.

The definition of an airliner varies from country to country, but the common definition is an aircraft with an empty weight above 22,680 kg (50,000 lb.), with two or more engines.

History of airliners

If an airliner is defined as a plane intended for carrying multiple passengers in commercial service, the Russian Sikorsky Ilya Muromets was the first official passenger aircraft. The Ilya Muromets was a luxurious aircraft with an isolated passenger saloon, comfortable wicker chairs, bedroom, lounge and a bathroom. The aircraft also had heating and electrical lighting. The Ilya Muromets first flew on December 10, 1913. On February 25, 1914, it took off for its first demonstration flight with 16 passengers aboard. From June 21June 23, it made a round-trip from Saint Petersburg to Kiev in 14 hours and 38 minutes with one intermediate landing. If it had not been for World War I, the Ilya Muromets would have probably started passenger flights that same year.

The second airliner was the Farman F.60 Goliath from 1919, which could seat up to 14 passengers. Approximately 60 were built. It was followed in 1923 by a less successful quad-engine Farman F.121 Jabiru.

The Ford Trimotor was an important early airliner. With two engines mounted on the wings and one in the nose and a slabsided body. It carried eight passengers and was produced from 1925 to 1933. It was used by the predecessor to TWA as well as other airlines long after production ceased. In 1932 the 14-passenger Douglas DC-2 flew and in 1935 the more powerful, faster, 21–32 passenger Douglas DC-3. DC-3s were produced in quantity for WWII and sold as surplus afterward.

The first jet airliners came in the immediate post war era. Turbojet engines were trialled on piston engine airframes such as the Avro Lancastrian and the Vickers VC.1 Viking the latter becoming the first jet engined passenger aircraft in April 1948. The first purpose built jet airliners were the de Havilland Comet (UK) and the Avro Jetliner (Canada). The former entered production and service while the latter did not. The Comet was unfortunate in that metal fatigue caused crashes.

Jets did not immediately replace piston engines and many designs used the turboprop rather than the turbojet or the later turbofan engines.

Types of airliners

Wide-body jets

The largest airliners are wide-body aircraft jets. These aircraft are frequently called twin-aisle aircraft because they generally have two separate aisles running from the front to the back of the passenger cabin. Aircraft in this category are the Boeing 747, Boeing 767, Boeing 777, Airbus A300/A310, Airbus A330, Airbus A340, Airbus A380(which can hold up to 800 passengers), Lockheed L-1011 TriStar, McDonnell Douglas DC-10, McDonnell Douglas MD-11, Ilyushin Il-86 and Ilyushin Il-96. These aircraft are usually used for long-haul flights between airline hubs and major cities with many passengers. Future wide-body models include the Boeing 787 and Airbus A350.

Narrow-body jets

A smaller, more common class of airliners are the narrow-body aircraft or single aisle aircraft. These smaller airliners are generally used for medium-distance flights with fewer passengers than their wide-body counterparts.

Examples include the Boeing 717, 737, 757, McDonnell Douglas DC-9 & MD-80/MD-90 series, Airbus A320 family, Tupolev Tu-204, Tu-214, Embraer E-Jets 190&195 and Tu-334. Older airliners like the Boeing 707, 727, McDonnell Douglas DC-8, Fokker F70/F100, VC10, Tupolev, and Yakovlev jets also fit into this category.

Regional airliners

Regional airliners typically seat fewer than 100 passengers and may be powered by turbofans or turboprops. These airliners, though smaller than aircraft operated by major airlines, frequently serve customers who expect service similar to that offered by crew on larger aircraft. Therefore, most regional airliners are equipped with lavatories and have a flight attendant to look after the in-flight needs of the passengers.

Typical aircraft in this category are the Embraer ERJ, Bombardier CRJ series and "Q" (DASH-8) series, ATR 42/72 and Saab 340/2000. Airlines and their partners sometimes use these for short flights between small hubs, or for bringing passengers to hub cities where they may board larger aircraft.

Commuter aircraft

Passenger aircraft with 19 or fewer passenger seats are called commuter aircraft or air taxis, depending on their size, engines, and seating configurations. The Beechcraft 1900, for example, has only 19 seats. Depending on local and national regulations, a commuter aircraft may not qualify as an airliner and may not be subject to the regulations applied to larger aircraft. Members of this class of aircraft normally lack such amenities as lavatories and galleys and typically do not carry a flight attendant as an aircrew member.

Other aircraft in this category are the Fairchild Metro, Jetstream 31/41, IPTN CN-235, and Embraer EMB 110 Bandeirante. The Cessna Caravan, a single-engine turboprop, is sometimes used as a small airliner, although many countries stipulate a minimum requirement of two engines for aircraft to be used as airliners.

Twin piston-engined aircraft made by Cessna, Piper, Britten-Norman, and Beechcraft are also in use as commuter aircraft.


Until the beginning of the jet age, piston engines were common on propliners like the Douglas DC-3. Now nearly all modern airliners are powered by turbine engines, either turbofans or turboprops. Gas turbine engines operate efficiently at much higher altitudes, are far more reliable than piston engines, and produce less vibration and noise. Prior to the jet age it was common for the same or very similar engines to be used in civilian airliners as in military aircraft. In recent years, divergence has occurred so that it is now unusual for the same engine to be used on a military type as a civilian type. Usually military aircraft which share engine technology with airliners are transports or tanker types.

Airliner variants

Some variants of airliners have been developed for carrying freight or for luxury corporate use. Many airliners have also been modified for government use as "VIP" transports and for military functions such as airborne tankers (for example, the Vickers VC-10, Lockheed L1011, Boeing 707), air ambulance (USAF/USN McDonnell-Douglas DC-9), reconnaissance (Embraer ERJ 145, Saab 340, Boeing 737), as well as for troop-carrying roles.


Modern airliners are usually low-wing designs with engines mounted in underwing pods (usually two of them). For airliners, multi-engine design is mandated by some national regulations so that aircraft can continue to climb even in the worst case of power loss in one engine right after take-off. Another regulatory demand is that aircraft are able to fly a minimum specified amount of time after one engine fails in flight (see ETOPS).

The idea of mounting the engines underneath and to the fore of the wing was first implemented by Boeing with the B-47 bomber of the 1950s, with the realization that this would provide for lesser efforts on the wings and therefore allow for a lighter wing structure. After this feature proved successful, Boeing introduced it to its 707 airliner design and it has been increasingly adopted since.

Mounting the engines in underwing pods also makes physical access for maintenance quicker and easier compared to tail-mounted engines.

Additionally, low wing design helps keep the engine nacelles and refueling valves closer to the ground to simplify access and the wing's surface acts as a barrier to prevent the engines' noise from reaching the fuselage in-flight.

Both Airbus and Boeing use this common layout for all of their passenger aircraft and emerging manufacturers (e.g. Embraer and Sukhoi Superjet) follow the same scheme.

In a few special cases, where engine proximity to ground is detrimental (e.g. rural airfields with risk of foreign object damage or dirt), airliners will feature tail-mounted engines (e.g. MD-80 or Tu-334) or high-wing designs with underhung nacelles (e.g. BAE-146). These planes become rarer every year as almost all newly-built airliners have underwing nacelles. Tail-engined designs are mostly used by business jet manufacturers.

Future airliners may feature innovative delta-wing or lifting body outlines.


These include:

The international market for middle-sized and large-sized airliners is now divided between Airbus and Boeing, though Russian/former Soviet manufacturers still sell significant numbers of airliners to their traditional markets. Smaller-sized aircraft manufacturers include, in addition to these two, ATR, Embraer and Bombardier.

Notable airliners

Airliner recycling

As airliners are very expensive, most are leased out for times typically from 20 to 40 years. Very few go back into service after a long lease is up because evolving aerospace technology leaves older airliners unable to compete against newer machines that can be operated at a lower cost. Many end-of-service airliners end up in the Mojave Desert, at the Mojave Spaceport (also known as "The Airplane Boneyard"). From this, the term "Mojave" has come to refer to the temporary storage of aircraft, e.g. during decreased demand for air travel and between short-term leases. Another airliner retirement location is Marana, Arizona.

While almost every airliner will be reduced to scrap (the exceptions end up as museum pieces or flown by collector groups) they may pass through many owners before they are retired. A well-maintained airliner can operate safely for decades, depending on how often it is flown, its operating environment, and whether damage and wear and tear is properly repaired.

What may end an airliner's working life is a lack of spare parts, as the original manufacturer and third manufacturers may no longer provide or support them. Corrosion and metal fatigue are other issues that become more expensive to deal with as time goes on. Eventually, these factors and advances in aircraft technology lead to older airliners becoming too expensive or inefficient to operate.

To protect the environment, the Airbus company has set up a centre in France to decommission and recycle older aircraft. More than 200 airliners will finish active life each year, and will be dismantled and recycled under the newly established PAMELA Project.

Cabin configurations and features







Overhead bins

The overhead bins are used for stowing carry-on baggage and other items. While the airliner manufacturer will normally supply a standard product, airlines may choose to have bins of differing size, shape, or color installed. Over time, these bins evolved out of what were originally overhead shelves used for little more than coat and briefcase storage. As concerns about falling debris during turbulence or in accidents increased, enclosed bins became the norm. Bins have increased in size in order to accommodate the larger carry-on baggage passengers may bring onto the aircraft. New bin designs may include a handrail, useful when moving through the cabin.

Passenger service units

Above the passenger seats are Passenger Service Units (PSU). These typically contain a reading light, air vent, and a flight attendant call button. The units frequently have small "Fasten Seat Belt" and "No Smoking" illuminated signage and may also contain a speaker for the cabin public address system.


Cabin pressurization

Airliners developed since the 1940s have had pressurized cabins (or more accurately, pressurized hulls including baggage holds) to enable them to carry passengers safely at high altitudes where low oxygen levels and air pressure would otherwise cause sickness or death. High altitude flight enabled airliners to fly above most weather systems that cause turbulent or dangerous flying conditions, and also to fly faster and further as there is less drag due to the lower air density. Pressurisation is applied using compressed air, in most cases bled from the engines, and is managed by a environmental control system which draws in clean air, and vents stale air out through a valve.


To maintain a pressure in the cabin equivalent to an altitude close to sea level would, at a cruising altitude around 10,000 m (33,000 feet), create a pressure difference between inside the aircraft and outside the aircraft that would require greater hull strength and weight. Most people do not suffer ill effects up to an altitude of 1800–2500 m (6000–8000 feet), and maintaining cabin pressure at this equivalent altitude significantly reduces the pressure difference and therefore the required hull strength and weight. A side effect is that passengers experience some discomfort as the cabin pressure changes during ascent and descent to the majority of airports, which are at low altitudes.

Cabin climate control

The air bled from the engines is hot and requires cooling by airconditioning units. It is also extremely dry at cruising altitude, and this causes sore eyes and dry skin and mucosa on long flights. Although humidification technology could raise its relative humidity to comfortable middle levels, this is not done since humidity promotes corrosion to the inside of the hull and risks condensation which could short electrical systems, so for safety reasons it is deliberately kept to a low value, around 10%.

Baggage holds

Airliners must have space on board to store baggage that will not safely fit in the passenger cabin.

Designed to hold baggage as well as freight, these compartments are called "cargo bins", "holds", or occasionally "pits". Occasionally baggage holds may be referred to as cargo decks on the largest of aircraft. These compartments can be accessed through doors on the outside of the aircraft. Despite what is seen in many movies, access doors between passenger cabins and baggage holds are rare in modern airliners.



Narrow-body airliners



Wide-body airliners

"Wide-body", or "jumbo jets", frequently have a compartment like the ones described above, typically called a "bulk bin". It is normally used for late arriving luggage or bags which may have been checked at the gate.




See also




External links and references

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