X-15 56-6670 was the first of three X-15s built by North American Aviation. On September 17th, 1959, North American Aviation Chief Engineering Test Pilot Albert Scott Crossfield made the first powered flight of an X-15 (tail number 56-6670) hypersonic research rocket plane. He reached Mach 2.11 (1,393 miles per hour/2,242 kilometers per hour) and climbed to 52,300 feet (15,941 meters). Over the next nine years and the three X-15s would make 199 flights, setting speed and altitude records. The first two X-15s, 56-6670 and 56-6671 survived the flight program however sadly 56-6672 broke apart on Flight #191.