North American X-15

The revolutionary X-15 remains the fastest manned aircraft ever to fly. Built in the two decades following World War II, it was the most successful of the high-speed X-planes. The only recently broken ''sound barrier'' was smashed completely by the X-15, which could hit Mach 6.7 and soar to altitudes above 350,000ft, beyond the edge of space. Several pilots qualified as astronauts by flying above ...