North American XF-108 Rapier

The North American XF-108 Rapier was a proposed long-range, high-speed interceptor designed by North American Aviation to defend the United States against supersonic Soviet bombers. It was to cruise near Mach 3 with a combat radius over 1,000 nautical miles, carrying radar and missiles able to engage bomber-sized targets at up to 100 miles. The programme shared engine development with the XB-70 Valkyrie bomber and reused elements of earlier interceptor studies. It never got beyond a single wooden mockup and was cancelled in 1959 for lack of funds and because the Soviet Union relied on ballistic missiles. Some design ideas passed to the North American A-5 Vigilante.