On October 14, 1947, over the Mojave Desert in California, US Air Force Captain Charles “Chuck” Yeager flew the rocket-powered Bell X-1 faster than the speed of sound. He was 24 years old. The aircraft carried the name Glamorous Glennis, after his wife, Glennis Faye Dickhouse. The flight ended years of speculation about an invisible “sound barrier” and opened the way to supersonic fighters, the Concorde and today’s quiet supersonic research jets.
What the “sound barrier” was
The speed of sound is not a fixed number. It depends on air temperature: about 761 mph at sea level on a mild day, but only about 660 mph at 40,000 feet, where the air is much colder. Engineers express speed relative to it as a Mach number; Mach 1 is the local speed of sound.
During World War II, fighter pilots diving at high speed ran into violent problems as they approached Mach 1. Air could no longer move smoothly out of the way; shock waves formed on the wings, the airplane shook, and controls became heavy or stopped working. Some aircraft broke apart. In September 1946, British test pilot Geoffrey de Havilland Jr. was killed when his DH 108 Swallow disintegrated during a high-speed run over the Thames Estuary. To many people, the sound barrier seemed like a physical wall.
The Bell X-1
The US Army Air Forces and the National Advisory Committee for Aeronautics (NACA), the predecessor of NASA, set out to build a research aircraft that could fly through the transonic zone and measure what happened. Bell Aircraft built the X-1.
- Shape: The fuselage was modeled on a .50-caliber machine gun bullet, a shape known to stay stable at supersonic speeds.
- Engine: A Reaction Motors XLR11 rocket engine with four chambers, burning ethyl alcohol and liquid oxygen. The pilot could fire the chambers one at a time. Fuel lasted only a few minutes.
- Launch: To save fuel, the X-1 did not take off from the ground. It was carried aloft in the bomb bay of a modified B-29 Superfortress and dropped.
- Tail: Its horizontal stabilizer could be adjusted in flight. This proved decisive, because it let the pilot keep pitch control when shock waves made the elevator ineffective.
October 14, 1947, step by step
- The B-29 took off from Muroc Army Air Field, a dry-lake test site that later became Edwards Air Force Base.
- Two nights earlier, Yeager had broken two ribs in a horse-riding accident. He told almost no one. Because the pain kept him from closing the X-1’s hatch with his right arm, engineer Jack Ridley cut him a piece of a broom handle to use as a lever.
- At about 20,000 to 25,000 feet, Yeager climbed down into the X-1, and the aircraft was released from the bomber.
- He fired the rocket chambers and climbed. At about 43,000 feet, the Machmeter jumped past 1. The X-1 reached Mach 1.06, roughly 700 mph at that altitude.
- Instead of violent shaking, the ride became smooth. On the ground, observers heard the first man-made sonic boom from an airplane in level flight.
- After the fuel ran out, Yeager glided down to land on the lakebed.
The flight was classified. News leaked to the trade press in December 1947, but the Air Force confirmed the achievement only in June 1948. Yeager, Bell president Lawrence Bell and NACA scientist John Stack received the Collier Trophy for 1947. The original Glamorous Glennis hangs today in the Smithsonian’s National Air and Space Museum in Washington, D.C.
Competing claims
Hans Guido Mutke, 1945
German pilot Hans Guido Mutke said he exceeded the speed of sound in a Messerschmitt Me 262 jet during a steep dive on April 9, 1945. There is no instrument record, and most experts believe the Me 262’s design could not have reached Mach 1. The claim remains unproven.
George Welch, 1947
North American test pilot George Welch, a World War II ace, flew dive tests in the prototype XP-86 Sabre in October 1947. Witnesses reported booms, and some historians believe he may have gone supersonic in a dive before or around the time of Yeager’s flight. No reliable measurement exists, so Welch is not officially credited. Yeager’s flight counts as the first confirmed supersonic flight in level, controlled conditions.
Faster and higher after 1947
- November 20, 1953: Scott Crossfield became the first pilot to fly at Mach 2, in the Douglas D-558-II Skyrocket.
- December 12, 1953: Yeager reached Mach 2.44 in the Bell X-1A, then nearly lost his life when the aircraft tumbled out of control.
- October 3, 1967: William J. “Pete” Knight flew the North American X-15 to Mach 6.7, still the speed record for a crewed, winged powered aircraft.
In the 1950s, supersonic flight became routine for military fighters such as the F-100 Super Sabre, the first US production fighter able to go supersonic in level flight.
Supersonic passenger jets
- December 31, 1968: The Soviet Tupolev Tu-144 made its first flight, ahead of the Concorde. It carried passengers only briefly in the late 1970s.
- March 2, 1969: The British-French Concorde first flew at Toulouse. It entered service with British Airways and Air France on January 21, 1976, cruising at about Mach 2 and crossing the Atlantic in around three and a half hours.
- 1973: Because of sonic booms, the FAA banned civil supersonic flight over US land, which limited the Concorde to ocean routes.
- July 25, 2000: Air France Flight 4590 crashed after takeoff near Paris, killing 113 people. Concorde flights resumed in 2001 but ended for good in 2003.
The new generation
Designers now focus on reducing the sonic boom rather than simply going faster.
- Boom XB-1: On January 28, 2025, this privately developed demonstrator broke the sound barrier over the Mojave Desert, the first independently developed civil jet to do so.
- NASA X-59: Built by Lockheed Martin’s Skunk Works to turn the boom into a soft “thump,” it made its first flight in October 2025 and its first supersonic flight in June 2026.
- Regulation: In July 2026, the FAA proposed a rule that would replace the 1973 overland ban with a noise-based limit on sonic boom strength at the ground.
Milestones at a glance
| Year | Aircraft | Pilot or operator | Milestone |
|---|---|---|---|
| 1947 | Bell X-1 | Chuck Yeager | First confirmed supersonic flight, Mach 1.06 |
| 1953 | D-558-II Skyrocket | Scott Crossfield | First Mach 2 flight |
| 1953 | Bell X-1A | Chuck Yeager | Mach 2.44 |
| 1967 | X-15 | Pete Knight | Mach 6.7 |
| 1968 | Tu-144 | Tupolev | First flight of a supersonic airliner |
| 1976 | Concorde | British Airways, Air France | Start of scheduled supersonic service |
| 2003 | Concorde | British Airways, Air France | Retirement |
| 2025 | Boom XB-1 | Boom Supersonic | Civil demonstrator goes supersonic |
| 2026 | X-59 | NASA | First supersonic flight of the quiet demonstrator |
Frequently Asked Questions
Who was the first person to fly faster than sound?
Chuck Yeager, on October 14, 1947, in the Bell X-1. Earlier claims by Hans Guido Mutke and George Welch have never been verified.
How fast did the Bell X-1 fly?
Mach 1.06 on the record flight, about 700 mph at roughly 43,000 feet.
Why don’t airliners fly supersonic over the US?
A 1973 FAA rule bans civil supersonic flight over land because of sonic booms. In 2026 the FAA proposed replacing it with a noise-based standard.
Where is the Bell X-1 today?
At the Smithsonian National Air and Space Museum in Washington, D.C.
