Flight of the Valkyrie. Forty years ago to this day was the first flight of a huge Mach 3 aircraft, as big as a DC-10. The XB-70 Valkyrie lifted into the skies at Palmdale, California and embarked on an intensive testing program. After its role as a bomber was abandoned, NASA helped it build a mountain of research for the doomed Boeing 2707 SST. The XB-70 was an icon of an era in which technology was grandiose and inspiring, and anything seemed possible.