The history of the development of supersonic speed by manned aircraft began during the Second World War in the United States. In 1943, the U.S. Air Force, together with the National Aeronautics Advisory Center, agreed to create an experimental aircraft capable of breaking the sound barrier. The development was entrusted to the company Bell Aircraft.
The first two aircraft created under this program received the designation X-1. However, due to the insufficient power of the turbojet engines of the time, converted heavy B-29 bombers were used to deliver aircraft to altitude. For the first time, the X-1 aircraft overcame the speed of sound in the fall of 1947.
In 1949, Bell was commissioned to develop a new program, the X-2. Two planes were created, and both failed: the first crashed in the air with the B-50 carrier plane, and the second crashed in the final phase of the flight.
Later, a program was developed that received the designation X-15. The creation of rocket plans for this program was entrusted to North American. Flight tests of the first prototypes began in June 1959.