ALEXANDRIA, Va. – Sickening thuds, moans of pain, despairing pleas for mercy, and then a final, defiant “Allah is the greatest” resounded through a courtroom yesterday before a long silence as the heart-rending cockpit recording of United Airlines Flight 93 was played in public for the first time.

In the four years since the September 11 attacks, Flight 93 has entered American mythology because of the passengers and crew’s heroic attempt to fight back against the hijackers.

Yesterday, for 31 numbing minutes, the full horror of their ordeal was laid bare, from the last dying screams of one of the staff, who pleaded, “I don’t want to die,” to the final battle for control of the cockpit as the plane hurtled into the ground.

Amid the rapid interchange and against the backdrop of heavy static, it was not always clear what was happening. It was also not always clear who was speaking. But the initial sounds were unmistakably of the stabbing and probably murder of two members of the flight crew.

As the jury listened in stunned silence, prosecutors sought to complete the simulation of the doomed plane’s cockpit by displaying video footage of a flight simulator, which re-enacted Flight 93’s rapid descent from its cruising altitude and its final stomach churning lurches.

The tape was the most dramatic testimony yet in the sentencing trial of Zacarias Moussaoui, the self-confessed would-be suicide bomber.

It opens at 9:31 a.m., about three minutes after the four hijackers made their move, and the very moment the 33 passengers were officially informed of their plight.

There is a crackle of static and then one of the four hijackers, believed to be the pilot, Ziad Jarrah, announces: “Ladies and gentlemen. Here the captain, please sit down, keep remaining sitting. We have a bomb on board. So sit.”

It is about the last clear and calm utterance he or anyone else will be able to make.

From the outset, it is clear that the passengers were not inclined to obey. A voice shouts: “Don’t move. Shut up.” Then there is the sound of a scuffle and a clatter of metal, as if of tin trays. Then come more shouts, often repeated three or four times. “Sit, sit, sit down sit down sit down … That’s it. That’s it. That’s it. Down. Down.”

The loud seatbelt warning beep briefly drowns the shouts. A voice from air traffic control asks, “Is that United 93 calling?” Another hijacker yells, “In the name of Allah the most merciful the most compassionate.”

Then comes a rapid sequence of “No. No. No. No. No,” followed by a loud “Lie down. Lie down. Down. Down. Down” and the sounds of another scuffle in the cockpit as if the hijackers are trying to control someone.

A despairing male voice says: “Please, please, please …” then “please, please don’t hurt me,” then simply, “Oh, God.”

Moments later one of the hijackers says confidently, “No more.” But the showdown is not over. Another member of the crew, believed to be a flight attendant, is apparently still alive in the cockpit.

“Are you talking to me?” one of the hijackers shouts. “No, no, no,” the unidentified person says before repeating three times, “I don’t want to die.” Then there is a “no,” the sound of thumping and thuds, a moan, whimpers, and a long groan. Then more blows before someone declares: “That’s it.”

It is 9:37 a.m. The plane has completed its 180-degree turn from its original path west to San Francisco from Newark and is heading back east toward the hijackers’ target, the Capitol in Washington, D.C. “Everything is fine,” one of the hijackers says. “I finished.” He was clearly speaking too soon. For the next 10 minutes, there are intermittent sounds of scuffling, believed to be from the other side of the cockpit door, interspersed with anxious interchanges between the hijackers as they fumble with the controls.

“This green knob?” one asks in Arabic. “Yes, that’s the one,” another replies.

All the while, the plane is heading west. The drama in the courtroom was made more intense as the plane could be seen as a dot on a screen map speeding toward the Pennsylvania field where Flight 93 crashed at 10:02 a.m.

After a few minutes of apparent calm in the cockpit, bedlam erupts at 9:57 a.m. as the passengers start a sustained assault from the rear of the plane, where they had been earlier herded. There is a bang and a crash.

“Is there something?” a hijacker asks.

“A fight?”

“Yeah?”

The plane by now is down to 5,200 feet. “Let’s go, guys,” one of the hijackers shouts, followed by “Allah is the greatest” and loud grunts of pain.

The pilot throws the plane violently from side to side to throw the passengers off balance, but the attack gathers force against a backdrop of crashes, bangs, and the sound of breaking china and glass.

“Is that it? Shall we finish it off?” Jarrah, asks as the plane pitches up and down.

“No. Not yet. When they all come we shall finish it off,” replies another hijacker. Then someone shouts “I’m injured” before the recorder captures a clear sense of the spirit that helped to rally America after the September 11 attacks.

“In the cockpit, if we don’t we die,” a passenger shouts.

And then moments later a voice says: “Roll it.” It is unclear if it is an echo of the iconic “Let’s roll” rallying call of Todd Beamer, one of the ringleaders in the fight-back, or a command to rock the plane to overbalance the hijackers. There are more groans, more cries of pain, more frantic shouts, and then a high pitched hiss of static as the autopilot is turned off. Then a hijacker shouts “Allah is the greatest” and the plane smashes into the ground.

For relatives of the victims the experience was all the more intense as they, unlike the jurors, were able to listen via special amplified headphones.

A transcript was later released, but the recording will not be released because of relatives’ objections. Hamilton Peterson lost his father and stepmother on the flight. He said that via his amplified recording he heard two people “recognizing they were going to die.

“Later you can hear an individual speaking a foreign language being attacked or killed by the passengers and crew. I surmised he was guarding the cockpit from outside.”

He backed the death penalty for Moussaoui, rejecting the idea that if executed he might become a martyr.