The Boeing 737 is a short to medium range, single aisle, narrow body jet airliner. Originally developed as a shorter, lower-cost twin-engine airliner derived from Boeing's 707 and 727, the 737 has nine variants with the -600, -700, -800 and -900 currently in production.

Originally envisioned in 1964, the 737 first flew in 1967,and entered airline service in February 1968. The 737 is Boeing's only single-aisle, narrow-body airliner currently in production, sometimes serving markets previously filled by 707, 727, 757, DC-9 and MD-80/90 airliners.