Olson said his wife made no reference to the nationality or motive of the hijackers.

Barbara Olson had originally planned to take a Monday flight to Los Angeles but changed her plans to have breakfast with her husband Tuesday, his birthday.

The plane that crashed in Pennsylvania, United Airlines Flight 93, took off at 8:01 a.m. EDT from New Jersey's Newark International Airport, bound for San Francisco. On board the Boeing 757 were 38 passengers, two pilots and five flight attendants. The early stages of the flight seemed normal, with the plane charting a westerly course that brought it to northern Ohio.

But as the jet was flying due west just below Cleveland, it made a sharp U-turn. Radar tracked it passing just south of Pittsburgh.

At 9:58 a.m., a 911 operator in Pennsylvania's Westmoreland County received a call from a man who said he had locked himself in a bathroom on a hijacked airliner. "We are being hijacked, we are being hijacked," the man said over his cell phone.

At the same time, flight attendant CeeCee Lyles, a mother of four, dialed her cell phone and told her husband, a Fort Myers, Fla., policeman, that her flight was being taken over by hijackers.

The Westmoreland County dispatcher, Edward Milliron, said his office was taking information from the passenger in the bathroom when the line went dead.

"We lost them," he said. "Two or three minutes later, we lost them."

Milliron said area residents began calling to report that a passenger jet was flying low over their homes. The plane crashed at 10:06 a.m. in a rural area near Indian Lake, about 80 miles southeast of Pittsburgh.

"I felt it. My house was shaken by it. I thought a truck hit my house," said Rev. Sylvia Baker, who lives about two miles from the crash site. "When I saw it wasn't my house, I was sure it had to be my neighbor's house."

The plane went down in an open field near a coal strip mine outside Shanksville, a hamlet of 235 people nestled in the wooded hills of western Pennsylvania. Mark Stahl of nearby Somerset said it carved a large black hole in the field and that smoke and flames billowed out.

"I didn't know what to think. It was shocking," Stahl said.

Reporters said the crater was about 40 feet wide and more than 8 feet deep. The largest debris from the plane was no bigger than a phone book. The crater was cordoned off, and officials said the task of removing bodies and the debris would not begin until this afternoon.

After a briefing by the Marine Corps, Rep. James P. Moran (D-Va.) said the plane may have been turning toward Camp David or Washington targets in its flight path when it went down. The crash site was 85 miles northwest of Camp David in the mountains of Maryland.

Response to the tragedies came from a number of quarters, some calling for swift retaliation while others urged moving ahead cautiously.

Former Secretary of State James A. Baker III said the United States should strengthen its intelligence capabilities.

"In effect, we unilaterally disarmed our intelligence capabilities," Baker said. "We need human intelligence to penetrate these groups."

Richard Holbrooke, former U.S. ambassador to the United Nations, said it would take the cooperation of numerous countries, including Russia and states in the Middle East, to bring those responsible to justice.

"Any nation seen to harbor or aid and abet these people must be treated as co-equally responsible," he said.

Larry Johnson, a former State Department counter-terrorism official, said the United States must wage war against those who launched the attacks.