01/31/2009. The B-29-96-BW was converted to the "mothership" for the X-1 trials, later it also carried others, including the X-1B. Initially operated by the USAAF/USAF, when this picture was taken, both the B-29 and the X-1B were operated by NACA. The X-1B is preserved in the National Museum of the USAF. View also photo 3433 and 7904.