N381US. Credit to Superliner350. The Boeing 720 was an American narrow-body airliner produced by Boeing Commercial Airplanes. Announced in July 1957 as a 707 derivative for shorter flights from shorter runways, the 720 first flew on November 23, 1959. Its type certificate was issued on June 30, 1960, and it entered service with United Airlines on July 5, 1960. A total of 154 Boeing 720s and 720Bs were built until 1967.[citation needed] As a derivative, the 720 had low development costs, allowing profitability despite few sales.Compared to the 707-120, it has a length reduced by 8.33 feet (2.54 m), a modified wing and a lightened airframe for a lower maximum takeoff weight. Originally designed to be powered by four Pratt & Whitney JT3C turbojets, the initial 720 could cover a 2,800 nautical miles [nmi] (5,200 km; 3,200 mi) range with 131 passengers in two classes. The reconfigured 720B, powered by JT3D turbofans, first flew on October 6, 1960, and entered service in March 1961. It could seat 156 passengers in one class over a 3,200 nautical miles [nmi] (5,900 km; 3,700 mi) range. Some 720s were later converted to 720Bs specification. It was succeeded by the Boeing 727 trijet.