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 The 707-320B had the application of the JT3D turbofan to the Intercontinental, but with aerodynamic refinements. The wing was modified from the −320 by adding a second inboard kink, a dog-toothed leading edge, and curved low-drag wingtips instead of the earlier blunt ones. These wingtips increased overall wingspan by 3.0 ft. Takeoff gross weight was increased to . The 175 707-320B aircraft were all new-build; no original −320 models were converted to fan engines in civilian use. First service was June 1962, with Pan Am. The 707-320B Advanced is an improved version of the −320B, adding the three-section leading-edge flaps