The Boeing 737 is a short- to medium-range twinjet narrow-body airliner developed and manufactured by Boeing Commercial Airplanes in the United States. Originally developed as a shorter, lower-cost twin-engine airliner derived from the 707 and 727, the 737 has developed into a family of thirteen passenger models with capacities from 85 to 215 passengers. The 737 is Boeing's only narrow-body airliner in production, with the 737 Next Generation (-700, -800, and -900ER) and the re-engined and updated 737 MAX variants currently being built.
The 737 was originally envisioned in 1964. The initial 737-100 made its first flight in April 1967, and entered airline service in February 1968 at Lufthansa. Next, the lengthened 737-200 entered service in April 1968. In the 1980s Boeing launched the longer 737-300, −400, and −500 variants (referred to as the Boeing 737 Classic series) featuring CFM56 turbofan engines and wing improvements.
The Boeing 737 Next Generation (NG) was introduced in the 1990s, with a redesigned, increased span wing, upgraded "glass" cockpit, and new interior. The 737 NG comprises the 737-600, −700, −800, and −900 variants, with lengths ranging from 31.09 to 42.06 m (102 to 138 ft). Boeing Business Jet versions of the 737 NG are also produced. The 737 was revised again in the 2010s for greater efficiency, with the 737 MAX series featuring CFM LEAP-1B engines and improved winglets. The 737 MAX entered service in 2017.
The 737 series is the highest-selling commercial jetliner in history. The 737 has been continuously manufactured since 1967; the 10,000th was rolled out on March 13, 2018, a MAX 8 destined for Southwest Airlines, and over 4,600 orders are pending. Assembly of the 737 is performed at the Boeing Renton Factory in Renton, Washington. Many 737s serve markets previously filled by 707, 727, 757, DC-9, and MD-80/MD-90 airliners, and the aircraft currently competes primarily with the Airbus A320 family. As of 2006, there were an average of 1,250 Boeing 737s airborne at any given time, with two either departing or landing somewhere every five seconds.