Investigators Seek Answers on Plane Crash After D.C. Sonic Boom Scare

Federal authorities on Monday were investigating what caused a private aircraft to fly into restricted airspace over Washington, D.C., on Sunday, triggering a response by military jets that caused a sonic boom to be heard across much of the region before the small plane crashed in Virginia, killing all four people onboard.

The private business jet went down near Montebello, Va., the National Transportation Safety Board said. A spokeswoman for the Virginia State Police said in a statement on Monday that emergency responders were able to reach the wreckage on foot about four hours after receiving a report of a plane crash.

John Rumpel, who runs Encore Motors of Melbourne, a Florida-based company that owns the aircraft, said in a telephone interview on Monday that his daughter, Adina Azarian, his 2-year old granddaughter, her nanny and the pilot were on the plane and did not survive.

The plane, a Cessna 560 Citation V, crashed “almost straight down and at a high speed,” he said, adding that the impact caused a crater, and the wreckage was spread over 150 yards. Mr. Rumpel had said on Sunday that they were returning home to East Hampton, N.Y., after a four-day visit to his home in North Carolina.