Joe Walker with X-15

On January 17, 1963, NASA research pilot Joe Walker flew the X-15 rocket plane to an altitude of 271,000 feet, or 51 miles high, becoming the first civilian test pilot to exceed 50 miles altitude. The flight was a precursor to his record altitude flights in July and August of the same year, the latter of which rocketed the X-15 to an unofficial world altitude record of 354,200 feet or 67 miles, a record that stood for more than 40 years until broken by Scaled Composites' Space Ship One in 2004. Photo and caption credit: NASA