Maybe United 93’s writer/director Paul Greengrass got some of the verbal details wrong in his account of the fourth Sept. 11 plane that never reached its Capitol building target, as evidenced by the cockpit recordings recently played at the Zacarias Moussaoui trial. Maybe there will be fallout from the conspiracy theorists who believe the whole story of determined passengers overtaking the hijackers is an elaborate hoax intended to cover-up a military action. And maybe, as New York theater patrons reportedly shouted when trailers for the film appeared in local theaters, a movie version of these events is just “too soon.

This is the additional baggage that comes along with dramatizing any real-life story as emotionally scarring as the Sept. 11, 2001, terrorist attacks on the United States. Oliver Stone faced it when he turned the Kennedy assassination into JFK, and that pivotal moment was already nearly 30 years in the nation’s rearview mirror. Was it possible to appreciate a dizzyingly effective piece of cinema even if the filmmaker wasn’t dotting all the proper i’s and crossing the proper t’s'or, in Oliver Stone’s case, turning i’s and t’s into q’s and S’s? Can you separate the experience of watching United 93 from the question of whether or not Greengrass got it right or at the right time?

I can’t tell you if Greengrass got it right as a history lesson. And I can’t conceive of how it might be perceived by those whose loved ones are portrayed struggling and dying in an unimaginable situation. All I can say is that United 93 delivers an experience so intense and immediate that I literally felt myself sweating as events unfolded, a knot of anxiety churning in my stomach. It’s a devastating 105-minute cocktail of dread, frustration and inevitable tragedy.

Greengrass relates the events of that horrific day in a verité style that comes both from casting and technique. Real-life airline personnel play the flight crew of the doomed United Flight 93; real-life air traffic controllers, including National Air Traffic Control supervisor Ben Sliney, play themselves. Our knowledge of the events to come turns simple images and events into unnerving portents'a 30-minute flight delay will be the window that allows the passengers to hear news of the other hijacked flights, and shots of passengers entering the plane becomes a gallery of the dead walking.

But the real surprise of United 93 may be how little time the film actually spends on the titular flight. For long stretches, it becomes a procedural focusing on the way civilian air traffic controllers and military personnel respond to the rapidly unfolding crisis. Unconfirmed speculation spreads about exactly how many hijacked planes are out there; soldiers wait impotently for clearance to scramble jets. And there’s a clear swipe at the inability of North America Aerospace Defense Command commanders to track down the president for authority to shoot down aircraft. Though individuals are shown doing their jobs to the best of their ability in a previously inconceivable situation, the overall picture is a horror show of bureaucratic chaos punctuated only occasionally by the stark silence of watching another monument go up in flames.

There is, perhaps, something a bit simplistic in setting up the quickly focused uprising of the United 93 passengers as counterpoint to the confusion on the ground. It’s hard to mistake the subtext, yet Greengrass doesn’t dwell on it. Instead, he merely observes the organizers'folks like Mark Bingham (Cheyenne Jackson), Thomas Burnett (Christian Clemenson) and Todd Beamer (David Alan Basche)'as they throw together their impromptu strike plan and put it into action. He does take a few too many uncomfortable forays into grief porn as one passenger after another makes a final call to loved ones, but in every setting, Greengrass primarily concerns himself with yanking viewers into the middle of a nightmare.

Will moments in United 93 infuriate some viewers? Almost certainly. Perhaps it will be the suggestion that hijacker pilot Ziad Jarrah (Khalid Abdalla) hesitates, whether out of fear or conscience. Perhaps it will be the loaded juxtaposition of anguished passengers reciting the Lord’s Prayer while the terrorists invoke the name of Allah. Or, perhaps, its mere existence cuts too close for some, with a five-year anniversary not yet passed. All I know is that United 93'in that ineffable way that defines truly visceral moviemaking'simply works, in a way that feels honest and probing yet respectful. It’s an impact you can only feel in sweat, stomach knots and heartache.