The concept is similar to the escort fighter, but differs primarily in that the aircraft would not operate in close concert with bombers.
The presence of the North American P-51 Mustang above Germany allowed USAAF bombers to fly at will over the country, and is considered one of the turning points of the air war.
[1] The desire for a fighter that could penetrate enemy airspace along with the bombers led to several prototype designs in the early 1950s, including the McDonnell XF-88 Voodoo, Lockheed XF-90 and North American YF-93.
[2][3] The North American XF-108 Rapier project was for a long-range interceptor intended to launch from the continental United States and intercept Soviet bombers while still in the far Arctic.
This long range meant that if they were launched from forward bases in Europe, Turkey or Alaska, the F-108 would be able to travel a fair distance over the USSR and help disrupt the defences for the following North American XB-70 bombers.