Three airframes, with US Air Force serials 46-062, 46-063 and 46-064, were built under the terms of contract W33-038-ac-9183, which had been signed on March 16 1945. The three aircraft, which originally carried the XS (Experimental Supersonic) designation, would be used to explore the transonic speed envelope wherein an object transitions from subsonic to supersonic flight, with emphasis on the affects on stability and control experienced during supersonic flight.