The Boeing 737 is a short- to medium-range twinjet narrow-body airliner. Originally developed as a shorter, lower-cost twin-engined 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-engined and redesigned version, the 737 MAX, is set to debut in 2017.
The wing was redesigned with a new airfoil section, greater chord, increased wing span by 16 ft (4.9 m) and area by 25%, which increased total fuel capacity by 30%. New, quieter, more fuel-efficient CFM56-7B engines were used. The wing, engine, and fuel capacity improvements combined increase the 737's range by 900 nautical miles to over 3,000 nautical miles (5,600 km), now permitting transcontinental service.
The 737's main landing gear under the wings at mid-cabin rotates into wells in the aircraft's belly. The legs are covered by partial doors, and "brush-like" seals aerodynamically smooth (or "fair") the wheels in the wells. The sides of the tires are exposed to the air in flight. "Hub caps" complete the aerodynamic profile of the wheels. It is forbidden to operate without the caps, because they are linked to the ground speed sensor that interfaces with the anti-skid brake system. The dark circles of the tires are clearly visible when a 737 takes off, or is at low altitude.
Engines on the 737 Classic series (300, 400, 500) and Next-Generation series (600, 700, 800, 900) do not have circular inlets like most aircraft. The 737 Classic series featured CFM56 turbofan engines, which yielded significant gains in fuel economy and a reduction in noise over the JT8D engines used on the -100 and -200, but also posed an engineering challenge given the low ground clearance of the 737.
| Role | Narrow-body jet airliner |
|---|---|
| National origin | United States |
| Manufacturer | Boeing Commercial Airplanes |
| First flight | April 9, 1967 |
| Introduction | February 10, 1968, with Lufthansa |
| Status | In service |
| Primary users | Southwest Airlines Ryanair United Airlines American Airlines |
| Produced | 1966–present |
| Number built | 8,263 as of October 2014 |
| Unit cost | 737-100: US$32 million 737-600: US$59.4 million 737-700: US$78.3 million 737-800: US$93.3 million 737-900ER: US$99.0 million |
| Variants | Boeing T-43 |
| Developed into | Boeing 737 Classic Boeing 737 Next Generation Boeing 737 MAX |
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