North American XF-108 Rapier

The North American XF-108 Rapier was a proposed long-range, high-speed interceptor aircraft designed by North American Aviation intended to defend the United States from supersonic Soviet bombers. To limit development costs, the program shared engine development with the North American XB-70 Valkyrie strategic bomber program, and used a number of elements of earlier interceptor projects. The program had progressed only as far as the construction of a single wooden mockup when it was cancelled in 1959, due to a shortage of funds and the Soviet's adoption of ballistic missiles as their primary means of nuclear attack. Had it flown, the F-108 would have been the heaviest fighter of its era. Following the program's termination, the fire-control system, incorporating the Hughes GAR-9 missile, was adapted for the Lockheed YF-12, which was itself canceled.