During the early 1960s, the NASA Flight Research Center was involved in support of the national Supersonic Transport Program (SST). Two prototype Mach 3+ high altitude bombers, built by North American Aviation for the Air Force, became available for SST research with the cancellation of their intended military program. The XB-70A Valkyrie was the largest experimental aircraft, measuring 190 feet in length, with a wing span of 105 feet and standing 33 feet in height. The aircraft had a delta wing and hinged wing tip that could be folded down to a 65 degree angle to improve stability at the aircraft's supersonic speeds of up to Mach 3. At this speed the Valkyrie was designed to ride its own shock wave.

Unfortunately program got several serious setbacks including crash of other prototype which caused death of two pilots. After that whole project was abandoned... (Originally created under wrong name : Fri Apr 28 2000 at 10:16 utc)