Boeing KC-135 Stratotanker subclass of tanker aircraft
The Boeing KC-135 Stratotanker is an American military aerial refueling tanker aircraft that was developed from the Boeing 367-80 prototype, alongside the Boeing 707 airliner. It has a narrower fuselage and is shorter than the 707. Boeing gave the aircraft the internal designation of Model 717. The KC-135 was the United States Air Force's first jet-powered refueling tanker and replaced the KC-97 Stratofreighter. The KC-135 was initially tasked with refueling strategic bombers, but it was used extensively in the Vietnam War and later conflicts such as Operation Desert Storm to extend the range and endurance of US tactical fighters and bombers.
The KC-135 entered service with the United States Air Force (USAF) in 1957; it is one of nine military fixed-wing aircraft with over 60 years of continuous service with its original operator.  The KC-135 is supplemented by the larger McDonnell Douglas KC-10 Extender.  Studies have concluded that many of the aircraft could be flown until 2030, although maintenance costs have greatly increased. The KC-135 is to be partially replaced by the Boeing KC-46 Pegasus.
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