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 by a US carrier on October 30, 1983, although 707s remained in scheduled service by airlines from other nations for much longer. Middle East Airlines of Lebanon flew 707s and 720s in front-line passenger service until the end of the 1990s. Since LADE of Argentina took its 707-320Bs from regular service in 2007, Saha Airlines of Iran was the last airline to keep 707s in scheduled passenger service until April 2013. Operations of the 707 were threatened by the enactment of international noise regulations in 1985. Shannon Engineering of Seattle developed a hush kit with funding from Tracor, Inc, of