WIKIARCHIVES.SPACE

As crew members secure the X-15 rocket-powered aircraft after a research flight, the B-52 mothership used for launching this unique aircraft does a low fly-by overhead. The X-15s made a total of 199 flights over a period of nearly 10 years -- 1959 to 1968 -- and set unofficial world speed and altitude records of 4,520 mph (Mach 6.7) and 354,200. Information gained from the highly successful X-15 program contributed to the development of the Mercury, Gemini, and Apollo piloted spaceflight programs, and also the Space Shuttle program.