The KC-135 tanker is the U.S. Air Force’s first jet-powered tanker for refueling jets in flight.

The KC-135 has a twisted past. In 1954, the Strategic Air Command held a competition to replace the KC-97 tanker, which had been deemed unsuitable for refueling jets. A year later, Lockheed’s proposal to modify its L-193 as a refueling tanker was declared the winner.

But Boeing’s KC-135, an adaptation of Boeing’s 367-80 (commonly known as the “Dash-80”) into an aerial tanker, was already flying and could be delivered two years earlier than Lockheed’s proposal. Secretary of the Air Force, Harold Talbott, ordered the purchase of 250 KC-135s until Lockheed could build the adapted L-193s.

Eventually, the Air Force cancelled its order rather than support two tanker designs. Boeing has since dominated the U.S. airline industry and based its 707 model on the 367-80. The Air Force ended up with a fleet of 732 KC-135s, receiving its first tanker in 1957 and its last in 1965.

Although the KC-135 was originally designed to fuel strategic bombers during the Cold War, it ended up refueling jets during the Vietnam War.

Replacing the aging KC-135 has been a convoluted tale as well. The Air Force requested proposals in January 2007 and a year later selected the proposal by Northrup Grumman, partnered with the European Aeronautic Defence and Space Company, to adapt the Airbus A330 for refueling capability.

Boeing protested the selection and the U.S. Government Accountability Office agreed. The bidding process reopened in July 2008 but was closed again that September. A year later, the Air Force took steps to open the bidding process again, but by this time, Northrup Grumman had decided not to submit a bid. EADS, with the support of Arizona Senator John McCain, remains in the running.