Bell X-1

The Bell X-1, originally designated XS-1, was a joint NACA-U.S. Army Air Forces/US Air Force supersonic research project and the first aircraft to exceed the speed of sound in controlled, level flight. It was the first of the so-called X-planes, an American series of experimental aircraft designated for testing of new technologies and usually kept highly secret.

 NOT TO BE CONFUSED WITH THE BAND, Bell X1!