The Bell X-1 is a rocket engine–powered aircraft, designated originally as the XS-1, and was a joint National Advisory Committee for Aeronautics–U.S. Army Air Forces–U.S. Air Force supersonic research project built by Bell Aircraft. Conceived during 1944 and designed and built in 1945, it achieved a speed of nearly 1,000 miles per hour in 1948. A derivative of this same design, the Bell X-1A, having greater fuel capacity and hence longer rocket burning time, exceeded 1,600 miles per hour in 1954. The X-1 aircraft #46-062, nicknamed Glamorous Glennis and 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 rocket planes designed for testing new technologies.

An air speed record is the highest airspeed attained by an aircraft of a particular class. The rules for all official aviation records are defined by Fédération Aéronautique Internationale (FAI), which also ratifies any claims. Speed records are divided into multiple classes with sub-divisions. There are three classes of aircraft: landplanes, seaplanes, and amphibians; then within these classes, there are records for aircraft in a number of weight categories. There are still further subdivisions for piston-engined, turbojet, turboprop, and rocket-engined aircraft. Within each of these groups, records are defined for speed over a straight course and for closed circuits of various sizes carrying various payloads.