Editing Jet aircraft (section)

==Jet engines==
{{Main|Jet engine}}

There are several types of engine which operate by expelling hot gas:
[[File:Lockheed SR-71 Blackbird (modified).jpg|thumb|The [[Lockheed SR-71 Blackbird|Lockheed SR-71]] was one of the fastest jet flying at Mach 3.35 ({{cvt|3661|km/h}}]]
*[[turbojet]]
*[[turbofan]]
*[[ramjet]]
*[[turboprop]] 

The different types are used for different purposes.

Rockets are the oldest type, and are mainly used when extremely high speeds are needed, or operation at extremely high altitudes where there is insufficient air to operate a jet engine. Due to the extreme, typically [[hypersonic]], exhaust velocity and the necessity of oxidiser being carried on board, they consume propellant extremely quickly, making them impractical for routine transportation.

Turbojets are the second oldest type; they have a high, usually supersonic, exhaust speed and low frontal cross-section, and so are best suited to high-speed, usually supersonic, flight. Although once widely used, they are relatively inefficient compared to [[turboprop]] and turbofans for subsonic flight. The last major aircraft to use turbojets were Concorde and Tu-144 [[supersonic transport]]s.

Low bypass turbofans have a lower exhaust speed than turbojets, and are mostly used for high sonic, transonic, and low supersonic speeds. High bypass turbofans are relatively efficient, and are used by subsonic aircraft such as airliners.