“ XB-1 met all of its test objectives, including safely and successfully achieving an altitude of 7,120 feet and speeds up to 238 knots (273 mph).” So really a

“ XB-1 met all of its test objectives, including safely and successfully achieving an altitude of 7,120 feet and speeds up to 238 knots (273 mph).” So really a shakedown, didnt try for supersonic