A sonic boom over Washington: Breaking down the Cessna 560 Citation plane crash in Virginia

A pair of U.S. F-16 fighter jets caused a thundering sonic boom over Washington, D.C., as they tried and failed to contact the unresponsive pilot of a private Cessna jet that wandered into restricted airspace Sunday. The Cessna later lost altitude and crashed in a rural area of Virginia.

It's not yet known why the plane was over Washington, but it's possible a loss of cabin pressure rendered the pilot and passengers unconscious, the plane's owner said. The autopilot may have taken control.

The F-16s were scrambled from Joint Base Andrews to intercept the plane. The fighter jets did not cause the Cessna to crash, defense officials said.

The Cessna, identified as a Model 560 Citation, crashed near the George Washington National Forest near rural Montebello, Virginia, at about 3:23 p.m. No survivors were found.

The National Transportation Safety Board is investigating.

What is a sonic boom?

The F-16s were authorized to fly at supersonic speeds to reach the Cessna, the North American Air Defense Command said. Supersonic means the aircraft is flying at Mach 1, faster than the speed of sound. An aircraft moving at supersonic speed makes a noise comparable to thunder.

Sonic booms are shock waves produced by supersonic flight. When you hear a sonic boom, you're hearing a shock wave:

• Aircraft in flight push air aside, producing pressure waves of compressed and uncompressed air, similar to water waves created by a ship's bow.
• When an aircraft is flying below the speed of sound, the pressure waves move away from the craft in all directions.
• When the aircraft exceeds the speed of sound – at sea level, about 760 mph – these pressure waves collect in front of the craft and compress to form shock waves.
• As the aircraft accelerates, the shock waves move toward the ground in what's called a "boom carpet."
• As shock waves reach the ground, they trigger a change in air pressure and create a sonic boom.

Aircraft create sonic booms constantly while in supersonic flight but pilots can't hear them. A person on the ground moving at the same speed as the supersonic aircraft would hear booms continuously. A stationary person would hear only one as the aircraft passed overhead.

What happened to the Cessna pilot?

It's not yet known why the Cessna pilot was unresponsive. Authorities tried to contact the Cessna by radio and the F-16 jets fired flares to attract the pilot's attention.

Flightradar24 and FlightAware charted the Cessna's flight. Times are approximate:

• 1:13 p.m.: Cessna departs Elizabethton Municipal Airport in Elizabethton, Tennessee. Its destination is Long Island MacArthur Airport in New York.
• 2:29 p.m.: Cessna flies over MacArthur Airport without landing and turns south. It begins to fly south toward Washington.
• 3:05 p.m.: As Cessna approaches Washington's restricted airspace, two F-16 jets are sent from Andrews to intercept.
• 3:23 p.m.: Flight tracking sites indicate the Cessna goes into a rapid spiraling descent, dropping at a rate of more than 30,000 feet per minute before it crashes in the St. Mary’s Wilderness.
• 4 p.m.: Virginia State Police is notified of the crash. It takes nearly four hours for rescuers to reach the crash site on foot. No survivors are found.

The Cessna was registered to Encore Motors of Melbourne Inc., in Florida. John Rumpel, who runs the company, told The New York Times that his daughter, 2-year-old granddaughter, her nanny and the pilot were aboard the plane.

They were returning to their home in East Hampton on Long Island after visiting his house in North Carolina, he said.

How large is Washington's restricted airspace?

Washington has the most restricted airspace in the U.S., according to the municipal government. The FAA lists multiple control zones around the city, including:

• Special Flight Rules Area: Special requirements for flying within a 33-mile radius around the city.
• Flight-Restricted Zone: Extends about 17 miles around Ronald Reagan Washington National Airport.
• Prohibited Area 56: Restricted areas surrounding the White House, the National Mall, and the vice president's residence in Washington, D.C.

P-56A covers approximately the area west of the Lincoln Memorial (Rock Creek Park) to the east of the Capitol (Stanton Square) and between Independence Avenue and K Street up to 18,000 feet.

P-56B covers a small circle with a radius of about one nautical mile (about 1.2 statute miles) surrounding the Naval Observatory on Massachusetts Avenue up to 18,000 feet.

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CONTRIBUTING John Bacon, Tom Vanden Brook and Thao Nguyen, USA TODAY

SOURCE USA TODAY Network reporting and research; Associated Press; U.S. Air Force; Federal Aviation Administration; Flightradar24; FlightAware