Air liner

An airliner is a type of aircraft for transporting passengers and air cargo. Such aircraft are most often operated by airlines. Although the definition of an airliner can vary from country to country, an airliner is typically defined as an aircraft intended for carrying multiple passengers or cargo in commercial service.

The largest airliners are wide-body 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. These aircraft are usually used for long-haul flights between airline hubs and major cities with many passengers.

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

Regional airliners typically seat fewer than 100 passengers and may be powered by turbofans or turboprops. These airliners are the non-mainline counterparts to the larger aircraft operated by the major carriers, legacy carriers, and flag carriers, and are used to feed traffic into the large airline hubs. These regional routes then form the spokes of a hub-and-spoke air transport model.

The lightest (light aircraft, list of light transport aircraft) of short-haul regional feeder airliner type aircraft that carry 19 or fewer passenger seats are called commuter aircraft, commuterliners, feederliners, and air taxis, depending on their size, engines, how they are marketed, region of the world, and seating configurations. The Beechcraft 1900, for example, has only 19 seats.

Types
Wide-body airliners
The largest airliners are wide-body jets, also 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, Boeing 787, Airbus A300/A310, Airbus A330, Airbus A340, Airbus A350, Airbus A380, 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.

Narrow-body airliners
A smaller, more common class of airliners is the narrow-body or single-aisle aircraft. These smaller airliners are generally used for medium-haul flights with fewer passengers than their wide-body counterparts. Currently produced narrow-body airliners include the Airbus A220 and A320, Boeing 737, Embraer E-Jet, and Tupolev Tu-204/214.

Out-of production aircraft include the McDonnell Douglas DC-9 and its derivatives MD-80/MD-90 series and Boeing 717, using the same cabin cross-section as the Boeing 737, the 757, 727, and 707, its competitor the Douglas DC-8 or the Tupolev Tu-154, Ilyushin IL-18, and the Ilyushin IL-62.

Future narrow-body airliners include the Comac C919 and Irkut MC-21.

Regional, short-haul, and feederliner aircraft
Regional airliners typically seat fewer than 100 passengers and may be powered by turbofans or turboprops. These airliners are the non-mainline counterparts to the larger aircraft operated by the major carriers, legacy carriers, and flag carriers, and are used to feed traffic into the large airline hubs or focus cities. These particular routes may need the size of a smaller aircraft to meet the frequency needs and service levels customers expect in the marketed product offered by larger airlines and their modern narrow- and wide-body aircraft. Therefore, these short-haul airliners are usually equipped with lavatories, stand-up cabins, pressurization, overhead storage bins, and reclining seats, and have a flight attendant to look after the in-flight needs of the passengers during point-to-point transit routes.

Because these aircraft are frequently operated by smaller airlines that are contracted to provide ("feed") passengers from smaller cities to hub airports (and reverse) for a "major" or "flag" carrier, regional airliners may be painted in the liveries of the major airline for which they provide this "feeder" service, so the regional airlines may offer and market a seamless transition between the larger airline to smaller airline.

Typical aircraft in this category include the Bombardier CRJ and Embraer ERJ regional jets along with the Bombardier "Q" (DASH-8) series, ATR 42/72 and Saab 340/2000 turboprop airliners.

Commuterliners used by regional airlines and air taxi operators
The lightest (light aircraft) of short-haul regional feeder airliner type aircraft that carry 19 or fewer passenger seats are called commuter aircraft, commuterliners, feederliners, and air taxis, depending on their size, engines, how they are marketed, region of the world, 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 that may fall into this category are the Fairchild Metro, Jetstream 31, and Embraer EMB 110 Bandeirante. The Cessna Caravan and Pilatus PC-12 are single-engined turboprops, sometimes used as small airliners, 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 short-haul, short-range, commuter-type aircraft.

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