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,
Giles Guthrie in total. Guthrie resumed flying and captained proving flights of the VC10, including a transatlantic demonstration to Boston. BOAC were permitted to purchase two Boeing 707 freighters during 1965 and after taking full ownership of the BOAC-Cunard joint venture, the two Boeing 707 passenger jets which Cunard Line had contributed to the joint venture (through their Cunard Eagle Airways subsidiary) passed to BOAC. Passenger growth and load factors quickly increased under Guthrie's tenure, and he invested in larger aircraft with more passenger capacity than either the Vickers Super VC10 or the Boeing 707 could provide. Boeing and Pan American World