North American Aviation’s X-15 rocket plane reached 4,520 mph and climbed to 354,200 feet during a program that ran from 1959 to 1968, producing flight data NASA credits as foundational to later U.S.

The NASA X-15 rocket plane reached speeds of Mach 6.7 and altitudes of 300,000 feet, flying to the edge of space and back. This groundbreaking program helped define the boundary between aviation and ...