People living in and around the nation's capital experienced a rare, if startling, sound: a sonic boom.
The boom was heard Sunday after the U.S. military dispatched six fighter jets to intercept an unresponsive business plane flying over restricted airspace.
The Air Force gave the F-16s permission to fly faster than the speed of sound — something civilian aircraft rarely get to do — as the jets scrambled to catch up with the Cessna Citation. The result was a thunderous rumble that resonated across a metropolitan area that's home to more than 6 million people.
The business jet eventually crashed in rural Virginia, killing the pilot and three passengers.
Below is an explanation of what sonic booms are, their history in the U.S. and their potential future.
What is a sonic boom?
Sonic booms are heard on the ground when airplanes overhead fly faster than the speed of sound. That speed is typically about 760 mph (1,220 kph) near sea level, but can vary depending on the temperature, altitude and other conditions, according to the Congressional Research Service.
As the plane speeds through the air, molecules are pushed aside with great force, “and this forms a shock wave, much like a boat creates a wake in water,” according to NASA.
“When this line of shock wave passes by, listeners on the ground hear a very loud noise," according to an explanation from Australia's University of New South Wales.
The F-16s flying over Washington on Sunday were “probably trying to go as fast it could to catch up” with the wayward Cessna airplane, said Anthony Brickhouse, an associate professor of applied aviation sciences at Embry-Riddle Aeronautical University.
The F-16 Fighting Falcon can fly 1,500 mph (2,410 kph) or twice the speed of sound, known as Mach 2, according to the Air Force.
What is the history of supersonic travel — and sonic booms?
In 1947, test pilot Charles “Chuck” Yeager became the first person to fly faster than sound in an orange, bullet-shaped Bell X-1 rocket plane. His exploits were told in Tom Wolfe’s book The Right Stuff, and in the 1983 film it inspired.
In the movie, someone on the ground asks, “What's that sound?” as Yeager's plane flies above the Mojave Desert and breaks the sound barrier.
Interest in supersonic flight initially focused mostly on military planes, according to the Congressional Research Service. But it grew to include supersonic civil aircraft in the 1960s.
For example, the Soviet Union became the first country in 1968 to fly a supersonic passenger plane, the Tupolev TU-144. But a fatal crash at the 1973 Paris Air Show ended that ambition.
In 1963, the U.S. government announced a major program to develop a supersonic passenger aircraft. But serious problems soon surfaced, including massive development costs and doubts about financial viability. The program was terminated in 1971.
During the 1960s, NASA was tasked with helping to develop commercial supersonic aircraft and researched the effects of sonic booms. It found that people who experienced them were not happy with the loud sounds, describing them as “annoying,” “irritating” and “startling.”
In 1973, the Federal Aviation Administration prohibited supersonic flights over land, “based on the expectation that such flights would cause a sonic boom to reach the ground,” the Congressional Research Service wrote.
The Concorde, an Anglo-French supersonic jetliner, saw success for a number of years after making its first commercial flights in 1976. However, its ear-rattling sonic booms irritated people on the ground and led to restrictions on where the jet could fly.
In the U.S., the plane flew mainly over the Atlantic to New York and Washington. It could fly at twice the speed of sound. And it promised to revolutionize long-distance travel by cutting flying time from the U.S. East Coast to Europe from eight hours to three and a half hours.
The Concorde never caught on widely. The plane’s economics were challenging, and its sonic booms led it to be banned on many overland routes. Only 20 were built; 14 of which were used for passenger service.
In 2003, British Airways and Air France both stopped Concorde service.
Sonic booms are still heard in the U.S. from the nation's military aircraft. In 2021, a sonic boom from F-15 fighter jets caused widespread concern that there was an earthquake on the Oregon coast.
What is the future of supersonic passenger travel — and sonic booms?
In 2018, the Congressional Research Service noted a revival of interest in supersonic aircraft, with startups hoping new technology could make them quieter and profitable.
Since then, American Airlines and United have bought supersonic jets from manufacturer Boom Supersonic. The aircraft are still on the drawing board and years away from flying — and not all industry observers believe they'll be profitable.
Meanwhile, NASA's X-59 airplane is designed to fly faster than sound — but with drastically reduced noise — over land, according to an April blog post from the agency.
“People below would hear sonic ‘thumps’ rather than booms, if they hear anything at all,” NASA wrote.