Twinjet

A twinjet or twin-engine jet is a jet aircraft powered by two engines. Such configuration of an aircraft is the most popular today for commercial airliners, for fighters, and many other kinds, because while offering safety from a single engine failure, it is also acceptably fuel-efficient.

As of today, there are three most common configurations of twinjet aircraft. The first has a podded engine usually mounted beneath, or occasionally above or within, each wing, usually for standard narrow-body and wide-body airliners.

The second has one engine mounted on each side of the rear fuselage, close to its empennage, which is common among most business jets.

In the third configuration, both jet engines are within the fuselage, side-by-side, which is notable for being used on most fighters since the 1960s, and still continuing, for example in the Su-27 'Flanker', the F-15 Eagle, and the F-22 Raptor.

The first "twinjet" ever to fly was the April 1941-debuted German fighter prototype Heinkel He 280, flying with a pair of nacelled Heinkel HeS 8 axial-flow turbojets.

The twinjet configuration was originally suitable for the short-range narrow-body such as the DC-9 and Boeing 737. The Airbus A300 was initially not successful when first produced as a short-range widebody, as airlines operating the A300 on short haul routes were forced to reduce frequencies to try and fill the aircraft and so they lost passengers to airlines operating more frequent narrow body flights. However, thanks to the introduction of ETOPs that allowed twin-engine jets to fly long-distance routes that were previously off-limits to them, Airbus was able to further develop the A300 as a medium/long range airliner to increased sales, and Boeing launched its widebody twinjet, the Boeing 767, in response.

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