A 79th Air Refueling Squadron (79th AREFS) KC-10A Extender aircraft refuels a 7th Airlift Squadron (7th AS) C-141B Starlifter aircraft as the two planes fly above the clouds over northern California. The KC-10 Extender is an air-to-air tanker aircraft in service with the United States Air Force derived from the civilian DC-10-30 airliner. The KC-10 was the second consecutive McDonnell Douglas transport aircraft to be selected by the US Air Force following the C-9 Nightingale. Conversion to the KC-10 involved only minor modifications to the DC-10-30, the largest of which was the addition of a boom control station in the rear of the fuselage and extra fuel tanks under the main deck. First deliveries to the Strategic Air Command (then in control of AAR assets) commenced in 1981.