SHANKSVILLE, Pa. — Just before United Airlines Flight 93 crashed, a passenger telephoned his wife, told her the plane had been hijacked and said he and some others were going to "do something about it."

Authorities have not said whether passengers struggled with the hijackers and whether that sent the airliner carrying 45 people into a western Pennsylvania field instead of a high-profile target. Elsewhere, hijacked planes hit New York's World Trade Center and the Pentagon on Tuesday.

As investigators pieced together the events leading to the crashes, loved ones and others speculated Wednesday that the passengers or crew on Flight 93 might have thwarted the hijackers.

"It sure wasn't going to go down in rural Pennsylvania. This wasn't the target; the target was Washington, D.C.," said Rep. John Murtha, D-Pa. "Somebody made a heroic effort to keep the plane from hitting a populated area."

"I would conclude there was a struggle and a heroic individual decided 'I'm going to die anyway, I might as well bring the plane down here.'"

At least one phone call made from the doomed plane suggested that might be what happened.

Thomas Burnett told his wife, Deena, that "a group of us are going to do something," she said. Burnett learned of the World Trade Center attacks during the four phone calls he made to his wife, and calmly told her that he and other passengers would try to take action against the hijackers.

"He thought he was going to be home. He was going to solve this problem," Deena Burnett told reporters at her home in San Ramon, Calif., Wednesday.

The plane crashed about 80 miles southeast of Pittsburgh after first flying near Cleveland and then turning around. The plane was said to be flying erratically and losing altitude.

The FBI would not comment on speculation about a struggle on board.

U.S. officials have said on condition of anonymity that the Secret Service feared the hijackers may have been headed for Camp David, the presidential retreat in Maryland about 85 miles from the crash site.

But Murtha, an intelligence officer in Vietnam, played down those reports. "I just don't think it's that significant" a target, he said.

In Washington, Attorney John Ashcroft said each of the planes was seized by three to six hijackers armed with knives and box cutters. Some were trained as pilots in the United States, Ashcroft said.

Analysts said recovery of Flight 93's cockpit voice recorder could be key in determining what happened. FBI assistant agent in charge Roland Corvington said that more than 200 investigators were on the scene and that the search might continue for three to five weeks.

Corvington said it would be difficult to identify any human remains.

The plane left Newark, N.J., for San Francisco at 8:01 a.m. EDT Tuesday. As it approached Cleveland, radar showed the plane banked left and headed back toward Pennsylvania. Cleveland Mayor Michael White said air traffic controllers said they could hear screaming on a plane they were in communication with.

Dennis Fritz, the control tower chief at the John Murtha Johnstown-Cambria County Airport, about 20 miles from the crash site, said his tower got a call from Cleveland controllers warning that the plane was headed toward Johnstown and flying erratically.

The Cleveland tower said the plane had done some unusual maneuvers, including a 180-degree turn away from Cleveland, and was flying at a low altitude. Johnstown controllers also could not see the plane from their tower, leading them to believe the plane was already very low.

"We had no call signal and we had no tail number. We had no way of making contact with the plane," Fritz said.

From Johnstown, the plane veered south, Fritz said. A witness on the ground called the Westmoreland County 911 center to report a large aircraft flying low and banking from side to side.

A passenger who called 911 from his cell phone told dispatchers he was inside a locked bathroom on the plane. Dispatcher Glenn Cramer said the man repeatedly said, "We're being hijacked!"

"He heard some sort of explosion and saw white smoke coming from the plane and we lost contact with him," Cramer said. The man never identified himself.

Minutes later, the plane slammed into the ground, nose first.