The Douglas DC-10 was produced in three basic models, the Series 10 for domestic routes to 3,500 miles and the series 30 and 40 for extended range and intercontinental travel. DC-10s were modified as passenger/cargo convertible versions and as the KC-10 aerial tanker for the Air Force. In addition to the luxury and spaciousness inherent in its wide cabin, the three-engine DC-10 incorporated improvements in propulsion, aerodynamics, structure, avionics, flight control systems and environmental compatibility that advanced industry standards. Designed and built in Long Beach, Calif., production was started in January 1968 and first deliveries were in 1971. The last of the giants was delivered in 1990. By 1990, 386 commercial DC-10s were delivered, plus 60 KC-10 tanker/cargo models built for the U.S. Air Force.