Douglas X-3 Stiletto (signed)The twin turbojet X 3, the only one built, was designed to test features of an aircraft suitable for sustained flights at supersonic speeds and high altitudes. A secondary mission was to investigate the use of new materials such as titanium and to explore new construction techniques. The X 3 made its first test flight at Edwards AFB, California on October 20, 1952 and flew supersonically in June 1953. Unlike the X 1, X 2, and X 15 which were released