The high altitude high speed experimental rocket-powered research aircraft X-15 was built by North American Aviation and Reaction Motors in 1955-56 and it was operated by the U.S. Air Force and NASA as part of the X-plane series of experimental aircraft. The X-15 achieved altitude and speed records and still holds the official world record for the highest speed reached by a manned aircraft. Its first flight was on 8th of June 1959. Its maximum speed was 4,520 miles per hour (7,274 km/h), its maximum altitude was 67.0 miles (107.8 km), and it had a range of 280 miles (450 km). Three X-15s were built and flew a total of 199 test flights. Twelve test pilots flew the X-15.
The Crash of the F-100 piloted by Charles Bronson's character (LTC Lee Brandon) was footage of a real Fatal F-100 Accident, on 10 January, 1956. The footage is commonly known as the "Sabre Dance" film which highlighted an issue with Adverse Yaw under certain conditions that was a source of a lot of problems for the F-100. What was supposed to be an 11 Minute Flight, From Accepting a brand new F-100 at NAA's Palmdale facility, and a short hop to George AFB, Turned into an ordeal because of a Gear malfunction that resulted in a Divert to Edwards AFB, and the Death of Lt Barty Brooks., and this Short bit of footage has been incorporated in dozens of films, and Television shows. It's still a punch to the chest to realize what you're watching when it's not expected.
The first manned orbital space flight by the Soviet Union (as generically referenced in the film) was on April 12, 1961. This film was released in December of 1961. The first U.S. orbital space flight was not until February 20, 1962. Some of the narration and dialogue in the film regarding aerospace engineering at that time, while accurate, should be considered in light of this context. Nevertheless, the X-15 was a highly successful aerospace research project.
The film was aired on TV in 1979, released on VHS in 1983 and released on DVD in 2004.