AQM-60 Kingfisher

A decade before the SR-71 first flew; the US Air Force had a Mach 4.3 capable Ramjet which was created to test US Air Force’s own air defenses. The AQM-60 Kingfisher was so effective that the project was canceled to avoid embarrassing their air defenses any further. The man who designed it went on to create the SR-71 spy plane.