Minutes before the Crash

In the aftermath of Tuesday's tragedy, a picture is beginning to emerge of the last terrifying moments aboard the four hijacked aircraft. First details of the surprisingly low-tech operation came from passengers on board the doomed jetliners who managed to make harrowing mobile phone calls to their loved ones minutes before they crashed.

They described how the terrorists had forced all the passengers to the back of the planes and had stabbed stewardesses with small craft knives, apparently in an attempt to force the pilots to unlock the doors to the cockpits.

Businessman Peter Hanson, who was with his wife and young son on board the United Airlines flight that plunged into the World Trade Center, called his father in Connecticut. He just managed to say a stewardess had been stabbed, before being cut off, FBI sources have reported.

Alice Hoglan in San Francisco said her 31-year-old son, Mark Bingham, phoned her from aboard the Pennsylvania crash flight. He said: "We've been taken over. There are three men that say they have a bomb."

A stewardess on the plane that crashed into the World Trade Center managed to dial 911- the emergency telephone number - from her cell phone. She reported that she and a colleague had been attacked with a knife, American Airlines stated.

Barbara Olson, wife of the US Solicitor General and a commentator for CNN, was on board the American Airlines flight from Washington to Los Angeles. Shortly before the plane dove into the Pentagon, Olson called her husband. She told him the plane had been hijacked and that the terrorists were wielding knives and cardboard cutters. Just before she was disconnected, she urged her husband to contact the FBI.

Terror in the Skies

Terrorism experts have said it is feasible that the hijackers could have armed themselves with nothing more than small pocket knives. "The reason that knives have been chosen is because it would have reduced their security risks," said Mike Yardley, a former British army officer. "Remember, they are trying to pull this off four times - if they had risked firearms, if one person had been seized, the whole operation could have been compromised."It is even possible the hijackers boarded the plane without even bothering to conceal their weapons. Passengers on US domestic flights would not have had a pocket knife taken off them if it was small enough, said Mr Yardley.

Reports from those on board the planes suggested each aircraft was taken by a team of three hijackers. In each case, at least one of them is likely to have been a trained pilot who took over the controls to steer the planes on their lethal flight paths.

According to aviation experts, the hijackers on the American Airlines plane that crashed into the Pentagon were skilled enough to shut off the so-called "transponder", the instrument which measures speed and altitude and reports a plane's flight number and location back to ground control. As a result, only an hour after lift-off, the aircraft had disappeared from the radar screen, only to suddenly appear heading directly towards the White House. At the last minute, the plane made a 270-degree turn and dove into the Pentagon.