The Bell X-1 (Bell Model 44) is a rocket enginepowered aircraft, designated originally as the XS-1, and was a joint National Advisory Committee for AeronauticsU.S. Army Air ForcesU.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 (1,600 km/h; 870 kn) 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 (2,600 km/h; 1,400 kn) in 1954. The X-1, piloted by Chuck Yeager, was the first manned 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 (and non-rocket planes) designed for testing new technologies.

Brigadier General Charles Elwood Yeager ( YAY-gər, February 13, 1923 – December 7, 2020) was a United States Air Force officer, flying ace, and record-setting test pilot who in 1947 became the first pilot in history confirmed to have exceeded the speed of sound in level flight.

Yeager was raised in Hamlin, West Virginia. His career began in World War II as a private in the United States Army, assigned to the Army Air Forces in 1941. After serving as an aircraft mechanic, in September 1942, he entered enlisted pilot training and upon graduation was promoted to the rank of flight officer (the World War II Army Air Force version of the Army's warrant officer), later achieving most of his aerial victories as a P-51 Mustang fighter pilot on the Western Front, where he was credited with shooting down 11.5 enemy aircraft (the half credit is from a second pilot assisting him in a single shootdown). On October 12, 1944, he attained "ace in a day" status, shooting down five enemy aircraft in one mission.

After the war, Yeager became a test pilot and flew many types of aircraft, including experimental rocket-powered aircraft for the National Advisory Committee for Aeronautics (NACA). Through the NACA program, he became the first human to officially break the sound barrier on October 14, 1947, when he flew the experimental Bell X-1 at Mach 1 at an altitude of 45,000 ft (13,700 m), for which he won both the Collier and Mackay trophies in 1948. He then went on to break several other speed and altitude records in the following years. In 1962, he became the first commandant of the USAF Aerospace Research Pilot School, which trained and produced astronauts for NASA and the Air Force.

Yeager later commanded fighter squadrons and wings in Germany, as well as in Southeast Asia during the Vietnam War. In recognition of his achievements and the outstanding performance ratings of those units, he was promoted to brigadier general in 1969 and inducted into the National Aviation Hall of Fame in 1973, retiring on March 1, 1975. His three-war active-duty flying career spanned more than 30 years and took him to many parts of the world, including the Korean War zone and the Soviet Union during the height of the Cold War.

Yeager is referred to by many as one of the greatest pilots of all time, and was ranked fifth on Flying's list of the 51 Heroes of Aviation in 2013. Throughout his life, he flew more than 360 different types of aircraft over a 70-year period, and continued to fly for two decades after retirement as a consultant pilot for the United States Air Force.