Northrop X-4 Bantam
A tiny semi-tailless twinjet built by Northrop Aircraft Company under a 1946 Army Air Forces contract, to test whether deleting the horizontal tail would cure the stability problems of transonic flight. Two aircraft were built. The first was unreliable, flew only ten times and became a source of spare parts; the second carried the NACA programme from 1950 to 1953 and uncovered a growing pitch oscillation and three-axis hunting near Mach 0.9. NASA judges the type's importance to be a proved negative: the configuration did not suit speeds near Mach 1. Both aircraft survive in museums.