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 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.
X-15 was first broadcast on network TV in 1962.
The movies narrator, Jimmy Stewart, was an Air Force Brigadier General, he was the highest-ranking actor in American military history. He served for 27 years, officially retiring from the Air Force on May 31, 1968, when he reached the mandatory retirement age of 60.