The San Francisco-bound United Airlines passenger jet that crashed in western Pennsylvania shortly after 10 a.m. today had been diverted from its planned flight path and was heading in the general direction of Washington when it plunged to earth, killing all 45 persons aboard.

United Flight 93, originating in Newark, followed a seemingly normal course until it reached Cleveland, where it suddenly made a sharp turn south, followed by another turn toward the southeast, according to Federal Aviation Administration radar tracking reports. The reports were published on the Web by Flight Explorer at www.flightexplorer.com.

Leaders of Congress -- including Senate Majority Leader Thomas A. Daschle (D-S.D.), Senate Minority Leader Trent Lott (R-Miss.), House Majority Whip Tom DeLay (R-Tex.) and House Minority Leader Richard A. Gephardt (D-Mo.) -- were told at a briefing by the Capitol Police that the hijacked plane might have been bound for the Capitol or Camp David, the presidential retreat in Thurmont, Md., 85 miles southeast of the crash site, according to participants in the meeting.

The participants discussed the possibility of shooting down the aircraft, said Rep. Mike Pence (R-Ind.).

"The question I heard asked was: 'Who has the authority to order a commercial jetliner shot down by the military?' " Pence said. However, the congressional leaders soon learned that the plane had already crashed.

The North American Aerospace Defense Command (NORAD) issued a statement denying that United Flight 93 had been shot down by U.S. military aircraft.

Eyewitnesses near the crash scene said the plane, a Boeing 757-200 loaded with more than 11,000 gallons of fuel for the six-hour flight, flew low and then suddenly fell from the sky, producing a huge fireball and a 10-by-20-foot crater in a field near this rural Pennsylvania town, about 80 miles southeast of Pittsburgh.

"When it decided to drop, it dropped all of a sudden -- like a stone," said Tom Fritz, 63. Fritz was sitting on his porch along Lambertsville Road, about a quarter-mile from the crash site, when he heard a sound that "wasn't quite right" and looked up in the sky.

"It was sort of whistling," he said. "It was going so fast that you couldn't even make out what color it was."

The ensuing firestorm lasted five or 10 minutes and reached several hundred yards into the sky, said Joe Wilt, 63, who also lives a quarter-mile from the crash site.

"The first thing I thought it was, was a missile," Wilt said. The impact shattered a window in his basement and knocked down household objects from a shelf.

Westmoreland County emergency dispatchers said they received a last-ditch 911 cell phone call from a passenger at 9:58 a.m., just minutes before the crash. Dispatch supervisor Glenn Cramer told the Associated Press that the call came from a passenger who had locked himself inside one of the plane's lavatories. "We are being hijacked, we are being hijacked," Cramer quoted the caller from a transcript of the call.

The caller described the plane as "going down," Cramer told AP. "He heard some sort of explosion and saw white smoke coming from the plane, and we lost contact with him."

FBI agents quickly took possession of the tape of that 911 call, which constitutes the only public evidence so far of what went on during the doomed plane's last moments. The FBI declined to provide any information about the tape's contents or the identity of the caller. At the crash site, FBI Special Agent Jeff Killeen said he was unaware if there had been any communication from the pilot.

Authorities late today recovered the plane's flight-data and cockpit-voice recorders, government sources said. These should permit authorities to reconstruct what went on in the cockpit during the flight.

The FBI and Pennsylvania State Police cordoned off a huge area surrounding the crash site and blocked off all roads leading there. They permitted entry only to emergency vehicles and some members of the news media.

The woods surrounding the crash site was strewn with body parts, said local resident Fred Waugh, who was among the first on the scene. Waugh "got scared and left," he said. "I couldn't help nobody. I couldn't hear nobody."

United Flight 93 would have arrived at San Francisco International Airport at 11:14 a.m. Pacific time, after six hours and fourteen minutes in the air. Today's flight -- with 38 passengers, five flight attendants and two pilots on board -- was relatively empty; the Boeing 757-200's full capacity is 182 passengers. At the time of the crash, passengers should have been just finishing their breakfast, one of two meals they were to receive on board.

Emergency personnel examine the crash site of United Flight 93 near Shanksville, Pa. A man in the San Francisco-bound jet used his cell phone to call 911 just before the crash. "We are being hijacked," he reported.