Boeing 707 center section tanks. Its first flight was on January 11, 1958; 69 turbojet 707-320s were delivered through January 1963, the first passengers being carried (by Pan Am) in August 1959. The 707-420 was identical to the −320, but fitted with Rolls-Royce Conway 508 (RCo.12) turbofans (or by-pass turbojets as Rolls-Royce called them) of 18,000 lb (79 kN) thrust each. The first announced customer was Lufthansa. BOAC's controversial order was announced six months later, but the British carrier got the first service-ready aircraft off the production line. The British Air Registration Board refused to give the aircraft a certificate of airworthiness,
Boeing 707 fuselage and wing meant a painstaking redesign of the wing and landing-gear structures. Rather than spend money on upgrading the 707, engineer Joe Sutter stated the company "decided spending money on the 707 wasn't worth it". The project was cancelled in 1966 in favor of the newer Boeing 747. The 707-820 was a proposed intercontinental stretched variant of the 707-320B. It was to be powered by four Pratt & Whitney JT3D-15 turbofan engines and would have had a extension in wingspan. Two variations were proposed, the 707-820(505) model and the 707-820(506) model. The 505 model would have had a fuselage