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 that investigation are as follows: It was determined that the structure of the right horizontal stabiliser failed due to metal fatigue in the rear spar structure, and due to the lack of an adequate fail-safe structure or device should such an event occur. The investigation also identified deficiencies in the assessment of aircraft designs and their certification and in the way aircraft were inspected. The Boeing 707 320/420 series had an enlarged horizontal stabiliser (tailplane) assembly compared to earlier 707 aircraft, and in the redesign the increased loads on the tailplane structure had been taken by replacing some of the