<hi style=afpcap>One of the strangest special research types to emerge from the Douglas stable was the X-3 supersonic test vehicles. The X-3 was funded by the Air Force and made its first flight in October 1952 powered by two Westinghouse J34 engines. This was the last aircraft type in the Special research category designed by Douglas, who subsequently concentrated on multi engined airliners and military cargo planes, as well as light attack types such as the Navy A-4 Skyhawk.. </hi>