Republic XF-103

The Republic XF-103 was an American project for a powerful missile-armed interceptor aircraft that could destroy Soviet bombers while flying at speeds as high as Mach 3. In 1949 the United States Air Force issued a request for an advanced supersonic interceptor to equip the Air Defense Command, and a full-scale mock-up of the AP-57 was built and inspected in March 1953. Development was prolonged: work on the prototypes was delayed by continued problems with the titanium construction and, more seriously, by problems with the proposed Wright J67 engine, which never entered production. Republic suggested replacing it with the much less powerful Wright J65. The project was cancelled on 21 August 1957 with no flying prototype ever completed, so the aircraft never progressed past the mockup stage.