JUST before United Flight 93 crashed, some of the passengers learned of the attacks on the World Trade Centre and may have tried to overpower their hijackers to keep the jetliner from hitting another landmark.

Authorities have not disclosed whether there was a struggle aboard the plane carrying 45 people, and have not said what caused it to plunge into a Pennsylvania field.

But some of the victims telephoned relatives from the plane and said that they had resolved to wrest control of the flight back from their captors. Passenger Jeremy Glick, 31, telephoned his wife, Liz, after terrorists took over, Glick's uncle Tom Crowley said. She conferenced the call to an emergency dispatcher, who told Glick about the New York attacks.

"Jeremy and the people around them found out about the flights into the World Trade Centre and decided that if their fate was to die, they should fight," Mr Crowley said.

"At some point, Jeremy put the phone down and simply went and did what he could do" with the help of an unspecified number of other passengers, he said.

Among them was Thomas Burnett, a 38-year-old business executive from California. In a series of four mobile phone calls, Burnett had his wife, Deena, conference in the FBI and calmly gathered information about the other hijacked flights.

Burnett said 'a group of us are going to do something', his wife said, and he gave every indication that sacrificing the passengers wasn't part of their plan. "He was coming home. He was going to solve this problem and come back," she said.