Northrop X-4 Bantam

The Northrop X-4 Bantam was an American experimental jet aircraft of the late 1940s built to study the low-speed and transonic handling qualities of a semi-tailless, swept-wing design with no horizontal tail surface at all. Two examples were built and flown by the National Advisory Committee for Aeronautics at what is now Edwards Air Force Base, exploring how a tailless swept-wing aircraft behaved as it approached the speed of sound, particularly a longitudinal instability known as tuck-under that its research helped document. Though it never itself exceeded the speed of sound, the X-4 flight data informed later tailless and swept-wing aircraft designs and remains part of the early postwar X-plane research program that also produced the X-1 and X-5.