XF-103 RepublicThe XF 103 was developed as a high speed high altitude aircraft specifically designed to intercept incoming enemy bombers. The XF 103 was proposed in the same contract competition that resulted in the Convair F 102 Project MX 1554 Interceptor Fighter Airplane. The Republic design, Model AP 57, underwent a design performance evaluation conducted by the Air Material Command (AMC). The results showed an estimated top speed of 1438 knots. A limiting Mach