North American XB-70 Valkyrie

Courtesy NASA Originally conceived as a supersonic bomber, the North American XB-70A Valkyrie instead became the world’s largest experimental research aircraft, flying from September 21, 1964, until February 4, 1969. Two experimental prototypes of the XB-70A were under construction when the bomber program was canceled. At the same time there was growing interest in an American supersonic transport (SST), and the Valkyrie seemed a perfect testbed for SST research. The two prototypes were kept alive for