A KC-10 'Extender' tanker on display at the Grand Forks Air Force Base (GFAFB) 'Friends And Neighbors Day' on May 27th 1989. The McDonnell Douglas KC-10 Extender is an aerial refueling tanker aircraft - the military version of the three-engined DC-10 airliner operated by the United States Air Force (USAF). The KC-10 was developed from the Advanced Tanker Cargo Aircraft Program. It incorporates military-specific equipment for its primary roles of transport and aerial refueling. A total of 60 KC-10s were produced for the USAF. (Wikipedia)