The compact Northrop X-4 "Bantam" research aircraft was built by the Northrop Corporation for the National Advisory Committee for Aeronautics (NACA), forerunner to today's NASA, and the United States Air Force (USAF) to test aspects of flight as related to tailless aircraft design. Two prototypes were eventually completed with a first flight recorded on December 15th, 1948. Lacking true tail-area horizontal plane control surfaces, the design instead relied on a combination elevator/aileron arrangement (known as "elevons") to handle the aircraft's pitch and roll actions. The pair of aircraft proved troublesome throughout their test lives for their designs were generally unsound and unstable - recording just ten total flights from the period spanning 1950 to 1953.
As completed, the X-4 held an appearance akin to some fancy, sleek single-seat fighter envisioned by a comic book artist of the 1950s. The fuselage was well-rounded though purposely short with the swept-back wing mainplanes making up much of the aircraft's showcased surface area. In some ways, this design mimicked that as seen in the World War 2-era Messerschmitt Me 163 "Komet" rocket-powered interceptor which made an appearance in the latter half of the war. A twin-engine configuration was chosen for the X-4 which fitted 2 x Westinghouse J30-WE-7/9 series turbojet engines outputting at 1,600 lb thrust each and intakes set to either side of the cockpit. The tail unit held just the sole vertical fin and the undercarriage was a wheeled tricycle arrangement. Dimensions included a length of 7 meters, a wingspan of 8.2 meters, and a height of 4.5 meters. Performance from the two engines netted a maximum speed of 625 miles per hour, a range out to 420 miles, a service ceiling of 42,300 feet, and a rate-of-climb of 7,700 feet per minute.
Work on the tailless aircraft began with the formal contract given to Northrop on June 11th, 1946. By this time, World War 2 had been over for nearly a year and Northrop was furthering its interest in tailless flight through its collection of flying wings. As such, the marriage for this endeavor between the USAF and Northrop was in some ways fitting for the time. The initial test vehicle was delivered to USAF hands in November of 1948 and NACA began testing with the X-4 system in September of 1950.
Throughout its test life, the X-4 was modified and revised as required to help correct the many issues that permeated the product. The X-4 too was a product well-ahead of its time for the flight control systems of the day were limiting for the rather advanced design. The USAF began to look deeper into delta-wing configurations and eventually abandoned the idea of a tailless for the interim. The original X-4 aircraft was cannibalized to help along the second aircraft before the end.
The pair of X-4s were all that was made out of the short-lived Bantam program. The sole remaining example is currently (2015) found at the National Museum of the United States Air Force in Dayton, Ohio.