The museum's KC-135E was the first all-jet tanker assigned to the Air National Guard in April 1975, and it flew the last operational mission of any KC-135E on 14 July 2009.
In the early 1950s the Strategic Air Command (SAC) needed a refueling aircraft that could air refuel the B-52 Stratofortress. The refueler used at the time, the KC-97 Stratofreighter with piston engines, could not keep up with the B-52s in flight.
As a result, Boeing designed the jet-powered KC-135. The company also further refined the flying boom that it had developed in the late 1940s as a replacement for the slow hose system.
Originally equipped with four Pratt & Whitney J57 turbojet engines, the KC-135 was modified with TF33 turbofan engines in the 1980s. This modified tanker was designated the KC-135E. KC-135-Rs (the only KC-135 flown today) have CFM56 high-bypass turbofan engines which are quieter, cleaner, and more fuel efficient.
The KC-135 fleet, supplemented by the larger McDonnell Douglas KC-10 Extender, is scheduled to be replaced by the Boeing KC-46 Pegasus.