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,
El Al ("Starting Dec. 23, the Atlantic Ocean will be 20% smaller") to promote its non-stop transatlantic flights. This was a bold step: the airline industry had never used images of the ocean in its advertising because of the widespread public fear of airline crashes. The advertisement, which ran only once, proved effective. Within a year, El Al's sales tripled. Despite the purchase of its Britannias and inauguration of non-stop transatlantic flights the airline remained unprofitable. When Efraim Ben-Arzi took over the company in the late 1950s, the Britannias were replaced in the next decade by the Boeing 707 and Boeing 720