Another aircraft type that traces its ancestry to the 707 prototype is the U.S. Air Force KC/C-135 tanker-transport/cargo airplane. Boeing built 820 of these aircraft for the Strategic Air Command and the Military Air Transport Service (predecessor of the Military Airlift Command). The KC/C-135 series was initially designated within The Boeing Company as the model 717. In January 1998, the 717 model number was reassigned to the commercial line for the 717-200 regional jetliner.
Additionally, three 707-120s plus two 707-320Bs, designated VC-137s, were delivered to the Military Airlift Command for transporting high government officials. These 707s transported the President for more than 30 years until replaced in 1990 by two 747-200s designated as VC-25s.
Recent military applications of the 707 are the E-3 Airborne Warning and Control System or AWACS (used by the U.S. Air Force, NATO, the Saudi government and the French and British air forces for airborne surveillance, command and control) and the E-6 used by the U.S. Navy for submarine communications.
When the 707 production line was closed at the end of May 1991, Boeing had sold 1,010 of all types (not counting the KC-135 series).