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,
1977 Dan-Air Boeing 707 crash maintenance, and the aircraft had been flown for a considerable number of hours with the fault present. Over time the crack grew, until it was surmised, the damaged spar was no longer capable of carrying its designed load, whereupon the load was then taken over entirely by the front spar. The accident aircraft encountered several strong gusts during the approach immediately before the accident which, while not dangerous to a structurally sound Boeing 707, exceeded the load capable of being carried by the remaining intact spar on its own, leading to the spar eventually breaking and resulting in complete structural