The Boeing 737 is a short-to medium twin-jet narrow-body airliner. Originally developed as a shorter, lower-cost twin-engine airliner derived from Boeing’s 707 and 727, the 737 has developed into a family of nine passenger models with a capacity of 85 to 215 passengers.

The 737 is Boeing’s only narrow-body airliner in production, with the -700, -800 and -900ER variants currently being built. A re-engine and redesigned version, the 737 MAX, to debut in 2017. Originally envisioned in 1964, the initial 737-100 flew in 1967 and entered airline service in February 1968.

Next, the lengthened 737-200 entered service in April 1968. In the 1980s, Boeing launched the -300, -400 and -500 models, subsequently referred to as the Boeing 737 Classic series. The 737 Classics added capacity and incorporated CFM56 turbofan engines along with wing improvements. In the 1990s Boeing introduced the 737 Next Generation with multiple changes including a redesigned wing, upgraded cockpit and new interior.

The 737 Next Generation comprises the four -600, -700, -800 and -900ER models, ranging from 102 ft (31.09 m) to 138 ft (42.06 m) in length. Boeing Business Jet version of the 737 Next Generation are also produced.