Sonic boom updates: No survivors found after F-16 investigates unresponsive plane over DC

WASHINGTON -- D.C. Air National Guard F-16s were scrambled on Sunday from Maryland -- causing a sonic boom heard throughout large portions of Washington, D.C., and the surrounding area -- to investigate what the North American Aerospace Defense Command called an "unresponsive" Cessna business jet that had entered a restricted area over the nation's capital and ultimately crashed into a forest area of southwest Virginia.

"In coordination with the Federal Aviation Administration, NORAD F-16 fighter aircraft responded to an unresponsive Cessna 560 Citation V aircraft over Washington, D.C., and northern Virginia on June 4, 2023," a statement from NORAD's Continental U.S. Region said.

"The pilot was unresponsive and the Cessna subsequently crashed near the George Washington National Forest, Virginia," it added.

The Virginia State Police were en route to the crash site, which is located in a mountainous area of southwest Virginia.

There were four people aboard the Cessna that had originally taken off from Elizabethton, Tennessee, bound for Long Island MacArthur Airport in New York, the FAA said. No survivors were located, Virginia State Police said in a statement Sunday night.

A flight-tracking website showed the Cessna had flown at an altitude of 34,000 and reached Long Island, but it appears not to have landed -- instead heading back toward the D.C. area.

The F-16s scrambled from Joint Base Andrews just outside the nation's capital, an area that is always under tight flight restrictions. President Joe Biden was golfing at the base's golf course as the events unfolded, according to the White House.

NORAD said the fighter jets "were authorized to travel at supersonic speeds" so it could catch up to the Cessna after it flew over the D.C. area in what a U.S. official told ABC News was a strange flight pattern over the nation's capital.

In its statement, NORAD acknowledged that the sound that had startled D.C.-area residents around 3 p.m. ET was likely caused by the sonic boom created by the jets as they flew at supersonic speeds.

"During this event, the NORAD aircraft also used flares -- which may have been visible to the public -- in an attempt to draw attention from the pilot," the NORAD statement said.

NORAD said that when the Cessna was intercepted at approximately 3:20 p.m., "the pilot was unresponsive and the Cessna subsequently crashed near the George Washington National Forest, Virginia. NORAD attempted to establish contact until the aircraft crashed."

A U.S. official had previously told ABC News it appeared that the pilot at the controls of the Cessna had "passed out."

The FAA said in a statement that the Cessna appeared to have crashed at 3:30 p.m., 10 minutes after the F-16s had intercepted the jet.

Another U.S. official told ABC News the White House and U.S. Capitol were put on high alert but not "red alert," which would have triggered an evacuation.

The Virginia State Police said in a statement they were notified at 3:50 p.m. of "a possible aircraft crash in the Staunton/Blue Ridge Parkway region."

"Search efforts are still underway by state and local law enforcement," police said. "Nothing has been located at this time."

The FAA and National Transportation Safety Board will investigate what led the Cessna to crash.

Some aviation experts speculated that hypoxia may have incapacitated the pilot.

Hypoxia "occurs when there is not enough oxygen in the cabin," said Steve Ganyard, an ABC News aviation contributor. Ganyard said he believes Sunday's incident may be another example of hypoxia incapacitating those aboard the Cessna.

"The pressure should keep enough air in the cabin to stay alert and stay awake. In this case, it can happen insidiously where you lose consciousness, you begin to feel tingling, you get a sense of euphoria and it very slowly overcomes the people in the cabin," Ganyard said.

ABC News' Clara McMichael, Sam Sweeney and Davone Morales contributed to this report.