The McDonnell Douglas DC-10 is a three-engine jet airliner designed for medium to long range flights. Production began in 1968 and 368 commercial DC-10s were delivered before production ended in 1989. A total of six commercial models of the DC-10 were developed. The first, the Series 10, entered scheduled airline service for American Airlines and United Airlines in August 1971. Series 30 and Series 40 models with intercontinental range were introduced in 1972. The DC-10CF (convertible freighter) followed in 1973 and could be arranged to accommodate either passengers or cargo. In 1979, Series 15 was introduced with a combination of smaller airframe and more powerful engines for optimal performance in high-altitude airports in hot climates. Finally, Federal Express ordered the McDonnell Douglas DC-10 Series 30F, an all-cargo aircraft, which went into service in 1986. The DC-10 family of aircraft were designed with roomy cabin interiors and sophisticated climate control and pressurization systems allowing for separate temperature controls in different parts of the aircraft. They were also specifically designed to use existing airport facilities and to have quieter operation. The McDonnell Douglas KC-10 Extender was a military variant of the DC-10 and 60 of them were built and delivered to the U.S. Air Force between March 1981 and November 1988. Donald A. Gerds was a senior concept interior designer for Douglas Aircraft Company who worked on the DC series of aircraft.