Pittsburgh A United Airlines plane crashed Tuesday morning just north of the Somerset County Airport, the airline said.
Flight 93, a Boeing 757, was en route from Newark, N.J., to San Francisco. It was not immediately known how many people were aboard.
The plane crashed about 10 a.m. about 8 miles east of Jennerstown, according to county 911 dispatchers, WPXI-TV in Pittsburgh reported.
"It shook the whole station," said Bruce Grine, owner of Grine's Service Center in Shanksville, about 2 1/2 miles from the crash. "Everybody ran outside, and by that time the fire whistle was blowing."
United said it was also "deeply concerned" about another flight, Flight 175, a Boeing 767, which was bound from Boston to Los Angeles.
On behalf of the airline CEO James Goodwin said: "The thoughts of everyone at United are with the passengers and crew of these flights. Our prayers are also with everyone on the ground who may have been involved"
"United is working with all the relevant authorities, including the FBI, to obtain further information on these flights," he said.
The Somerset County airport, about 80 miles southeast of Pittsburgh, in a small, rural facility that does not handle large aircraft.
Because of attacks today at New York's World Trade Center, the Federal Aviation Administration had ordered all departing flights canceled nationwide, and any planes already in the air were to land a the nearest airport. The plane crashed shortly after the order was issued.