Concise history of the XB-70, including production, flight tests, and the fatal crash of Aircraft #2 in 1965. Aircraft #1 is now at the US Air Force Museum at Wright-Patterson AFB. The North American XB-70 is one of the most unusual looking aircraft in aviation history, and only two were constructed. It was originally designed as a Mach 3 high-altitude bomber, but was later used as a research aircraft.