Welcome to Warbird Wednesday! Today we are visiting a hypersonic rocket-powered aircraft, the North American X-15. This aircraft was part of the X-plane series and was a complete test bed. Dropping from a B-52, the X-15’s engine put out a total of 57,000 pounds-force of thrust, reaching the highest speed ever recorded, 4,520 miles per hour, or Mach 6.7! The X-15 could reach up to or exceed an altitude of 50 miles, qualifying it as the world’s first operational spaceplane, leading eight pilots to qualify as astronauts. The pilots who flew in this aircraft knew the risk that they were taking when getting in. Sadly, one of 12 pilots did not return. There were only three models built, all retiring by 1968.