WASHINGTON (NewsNation) — F-16 fighters scrambled Sunday at supersonic speed to intercept a private aircraft whose pilot was unresponsive as the plane violated restricted airspace above the Washington, D.C. area.

A Pentagon source tells NewsNation that a total of six F-16s were dispatched at the same time to try and intercept the Cessna 560 Citation V plane.

Two jets from Joint Base Andrews got there first, and attempted to make contact with the pilot for 30 minutes.

The Pentagon said the jets intercepted the plane and could not communicate with the pilot, even after attempting to make radio contact and using flares.

The two F-16s traveled at supersonic speeds, causing a sonic boom that was heard across the region. Military aircraft cause sonic booms when they travel very fast — either for testing and training purposes, or during emergencies, the Washington Post reported.

So, what exactly happened inside the plane that led up to that crash, and how was the military able to get those jets in the air so quickly?

It doesn’t take long to get jets in place to counter a possible threat in the air over D.C., especially after the 9/11 attacks. So, when a Cessna flew into a closed air space, the jets were authorized to intercept the small plane at supersonic speeds, causing a sonic boom audible for miles.

The Cessna’s citation’s flight path on FlightAware shows it took off from Tennessee Sunday afternoon just before 1 p.m., then flew up to Long Island before making a sharp u-turn, heading into the D.C. area, and crashing into the George Washington National Forest.

A U.S. Department of Defense official told NewsNation the jets did not shoot down the plane. It appears to have crashed on its own in rural southwest Virginia around 3:20 p.m. Sunday.

The National Transportation Safety Board said Monday that it will be at that crash site for days to determine what went wrong.

FAA records show the plane registered to Encore Motors of Melbourne, Inc., a Florida-based business. John Rumpel, who runs that company, said Sunday to the New York Times his daughter, two-year-old granddaughter, her nanny and the pilot were on board. The family was headed back to their house in the Hamptons after visiting Rumpel in North Carolina.

If the plane lost pressurization, Rumpel said to The Times, “they all just would have gone to sleep and never woke up.”

“It descended at 20,000 feet a minute, and nobody could survive a crash from that speed,” he said in the newspaper.

Virginia State Police said there were no survivors.

Officials have not yet released an official cause for the crash, but the suggestion from the plane’s owner about a loss of cabin pressure it echoes the 1999 plane crash that killed golf legend Payne Stewart. In that incident, a Learjet flew uncontrolled thousands of miles over the heartland before crashing in South Dakota.

Experts at the time said everyone on board was likely unconscious due to the loss of pressure, but with this Cessna investigation, it’s too early to know for sure.