The term penetration fighter was used for a short time to describe a theoretical long-range fighter aircraft designed to penetrate enemy air defences and attack defensive interceptors. The concept is similar to the escort fighter, but differs primarily in that the aircraft would not operate in close concert with bombers. This was, in effect, the same role played by the North American P-51 Mustang during World War II, whose presence above Germany allowed USAAF bombers to fly at will over the country.
The penetration fighter concept led to several prototype designs in the early 1950s, including the McDonnell XF-88 Voodoo, Lockheed XF-90 and North American YF-93. In order to be competitive with existing interceptors these had to be jet powered, this severely limited their range and demanded huge fuel loads. None proved able to compete with shorter range designs, and the penetration fighter concept faded.
The concept re-appeared with the North American XF-108 Rapier project, 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. The F-108 was ultimately cancelled in budget cuts, and its short-lived replacement, the Lockheed YF-12, was not considered in this role.
- Penetrator, the bomber equivalent
- "USAF Air Materiel Command Design 938A Penetration Fighter Study of 1948"
- Robert Lyons Jr., "The Search For An Advanced Fighter", US Air Force Air Command and Staff College, 1986
- "Fact Sheet: North American F-108A Rapier", National Museum of the United States Air Force