X-4 BantomNorthrop X 4 Bantom airplane model. The X 4, a single place, low swept wing, semi tailless aircraft was designed and built by Northrop Aircraft, Inc., for NACA. It had no horizontal tail surfaces, and its mission was to obtain in flight data on the stability and control of semi tailless aircraft at high subsonic speeds. The two X 4 aircraft were 23 ft long, 14 ft high, and had wingspans of 26 ft. They weighed almost 8,000 lb. at takeoff. Mahogany