Bell X-1
Breaking the sound barrier and beyond

The X-1 aircraft flown by Chuck Yeager, was the first piloted airplane to exceed the speed of sound in level flight and was the first of the X-planes, a series of American experimental planes designed for testing new technologies. The research techniques used for the X-1 program became the pattern for all subsequent X-plane projects. Later variants of the X-1 were built to test different aspects of supersonic flight.