Location of second United Airlines plane unknown

Two United Airlines jetliners crashed this morning, one in western Pennsylvania and the second at a location the airline did not immediately disclose.

A total of 110 people were aboard the two planes, the airline said.

One plane, United Flight 93, crashed north of the Somerset County airport, a

small airport about 80 miles southeast of Pittsburgh.

The Pennsylvania crash followed the crash of two planes into the World Trade

Center in New York City.

American Airlines initially said its planes crashed into the twin towers but later said that was unconfirmed.

"It shook the whole station," said Bruce Grine, owner of Grine's Service Center in Shanksville, about 2½ miles from the crash.

"Everybody ran outside, and by that time the fire whistle was blowing."