The McDonnell Douglas KC-10 Extender is an air-to-air tanker aircraft in service with the United States Air Force (USAF), 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. The similar KDC-10 is in service with the Royal Netherlands Air Force.
The KC-10 Extender was born out of the need to supplant the Boeing KC-135 Stratotanker. During the Vietnam War, doubts began to be raised regarding the 700 plus KC-135s' ability to meet the needs of the US' global commitments. The aerial refueling fleet was deployed to Southeast Asia in support of tactical aircraft and strategic bombers, while maintaining the US-based support of the nuclear bomber fleet. Consequently, the Air Force sought an aerial tanker with greater capabilities than the KC-135.
The KC-10 was delivered to the USAF Strategic Air Command (SAC), then in control of air refueling assets from 1981 to 1987. SAC had KC-10 Extenders in service from 1981 until 1992, when they were re-assigned to the newly established Air Mobility Command. In the air-to-air refueling (AAR) role, the KC-10s have been operated largely in the strategic refueling of large number of tactical aircraft on ferry flights and the refueling of other strategic transport aircraft. Conversely, the KC-135 fleet has operated largely in the in-theater tactical role.
There are 59 KC-10 Extenders in service with the USAF as of 2010. The KC-10 has a significantly larger fuel capacity than the Air Force's other main tanker, the KC-135. The USAF's KC-10s are stationed primarily at Travis AFB, California and McGuire AFB, New Jersey.
When faced with refusals of basing and overflight rights from continental European countries during Operation El Dorado Canyon, the U.S. was forced to use the UK-based F-111s in the 1986 air-strikes against Libya. The KC-10s allowed 29 F-111s to reach their targets. The KC-10 fleet also facilitated the deployment of tactical, strategic, and transport aircraft to Saudi Arabia during Operation Desert Shield. In recent times, USAF KC-10s have seen use in supporting military operations in Iraq and Afghanistan through 2009. In addition to offering in-flight refueling capabilities, USAF KC-10s also undertake cargo and personnel transport operations
Source: Wikipedia, "McDonnell Douglas KC-10 Extender", available under the CC-BY-SA License.