The North American X-15 was an experimental hypersonic rocket plane from 1989 which would skim along the edge of space to gather data. The few pilots that flew this craft were eventually rewarded with their astronaut wings as they had technically breached into space. In 1967 it set a new speed record for manned powered flight reaching a whopping Mach 6.7 (4520mph), which still holds strong today, double of the SR-71 at 2nd place!