Heroes stand up even in the hour of their deaths.(Chicago Tribune)

They waited, the way people wait on a plane.

You can picture them spreading out inside this mostly empty flight to San Francisco, the smokestacks and cranes of the Newark skyline looming outside their windows.

You can hear them working their cell phones, calling their friends, their offices.

For 41 minutes they waited on the tarmac to take off. Two pilots, five flight attendants and 37 passengers. Among them, four men knew they were all waiting to die.

When United Flight 93 finally took off, it began a journey that would not end in San Francisco, as planned, nor smashing into some Washington target, but in an aching glory.

Since Sept. 11, the story of the passengers who fought their hijackers on Flight 93 has become an icon of good thwarting evil, a story of sacrifice and courage that a nation has embraced in a time of fear and uncertainty.

No one will ever know exactly what happened on that plane. But new interviews with the family, friends and co-workers of passengers who made last-minute calls give a more complete account of their desperate struggle.

At the same time, questions emerge about the role of the fourth hijacker and raise the possibility that instead of a single plot to overcome the terrorists, passengers and flight attendants in different parts of the plane may have hatched separate plans. While most attention has focused on a group of tall, athletic men who apparently planned to rush the hijackers, at least one flight attendant told her husband she was boiling water to use as a weapon.

The clues from the wreckage are small: a knife concealed inside a cigarette lighter, a manual of prayers and instructions written in Arabic, a cockpit-voice recorder, still under analysis, that reportedly portrays a garble of American and Arabic voices.

But the key to whatever took place on Flight 93 may be the 41 minutes it sat on the ground.

It gave the passengers enough time to hear about the three other hijacked planes that smashed into the World Trade Center and Pentagon that morning.

The delay took the plane off the precise schedule the terrorists had likely relied upon and put it on one that gave the passengers and crew knowledge, knowledge that incited them to fight back and to say goodbye to loved ones before the jet plunged into a reclaimed strip mine in Pennsylvania, taking with it everyone aboard.

It was 5 a.m. Tuesday and still dark when Deborah Welsh's husband carried her bag down the stairs of their …