To the Cold War aviation engineers, speed was everything. So it is not surprising that as early as 1949 the USAF was issuing contracts to prototype Mach 3 interceptors. In fact the XF-103 was also known as the 1954 Interceptor, an all-weather radar equipped weapons platform for air to air missiles. Product failures and other delays with the Wright J67 engine put the first developed prototype on the runway in 1957. Titanium construction delayed the project until it was completely rethought and became the F-108 Rapier that added one more characteristic: it was a high altitude bomber that could operate at over 60,000 feet.
The project was cancelled but the Rapier mockup helped develop and sell the North American A-5 Vigilante, a carrier launched transonic bomber that was used quite a bit over Vietnam.