#TBT The XB-70 Valkyrie was the largest x-plane. Capable of flight at speeds three times the speed of sound (2,000 miles per hour) and altitudes of 70,000 feet, the XB-70 was used to collect in-flight information for use in the design of future supersonic aircraft.This video shows an XB-70A taking off from Edwards Air Force Base. To learn more about the XB-70 Valkyrie, visit: http://go.usa.gov/ct2aT | NASA's Armstrong Flight Research Center