Boeing 720

The Boeing 720 was a four-engine narrow-body jet airliner, announced in July 1957 as a shorter-range, shorter-runway derivative of the Boeing 707. It is about 2.5 metres shorter than the 707-120 and has a modified wing with Krueger flaps and a lightened airframe. The first aircraft flew on November 23, 1959 and United Airlines began service on July 5, 1960 with JT3C turbojets. The 720B, with more powerful JT3D turbofans, followed in 1960 and 1961. Because it reused so much of the 707, development cost was low and the 154 aircraft built from 1959 to 1967 were profitable. The Boeing 727 trijet then replaced it, and later owners used examples as engine testbeds and charter aircraft.