"We have some planes..."
So it began. A horror-show of televised hellfire, pumped out to mounting global uproar. To observers, it seemed like the opening offensive of World War Three. How must it have felt for those on board?
With the fifth anniversary of the 9/11 attacks approaching, director Paul Greengrass has spoken of the need to de-sensationalise; to train a steady gaze on the over-familiar, in a hunt for "the DNA of our times".
And so, with the blessings of most of those left bereft by the terrorists' contorted arrogance, he has crafted a ferocious, reverential requiem that squints for truth through tears of rage.
Where some lurid TV counterparts cocked a ghoulish, tabloid ear to the terrible intimacy of those goodbye calls, United 93 understands that subtlety and restraint are both more respectful and more gripping.
Rather than rudely jostle us into the midst of the madness, Greengrass is sly and gentle; gradually, surgically escalating the empathy with crushing glimpses of everyday mundanity - until the final, inevitable, barely watchable, five minutes of unrefined pandemonium.
His use of real air-traffic controllers lends naturalistic bite to the already urgent action. The drama is retched up from their disorder, as they clamour to decode the impassive graphics swarming across their screens.
Similarly, unknown actors keep the focus off the strong or the weak or the exaggerated good. Wesley Snipes is not going to stand up and make it all go away.
United 93's emphasis stays locked on the trivia of real people's hopes and habits and ordinary dreams: the captain slurps his orange juice and looks forward to a holiday; a member of the cabin crew bitches about working hours; another talks of missing her "babies" back home...
Greengrass' frenzied, hand-held style keeps the mood on the edge of jangling tension and mid-air suspension. By weaving in news footage, enactments of phone transcripts and recordings of actual cockpit chatter, the film is cast in a dreadful new dimension - beyond drama, beyond documentary.
We're looking at a kind of reconstruction, but hearing and experiencing real terror, real trauma. We're being guided by ghosts.
Having made 2002's devastating TV dramatisation, Bloody Sunday, Greengrass is no stranger to politically charged challenges and, with such a bright, emotive spotlight trained on his ethics and motivations, he's to be commended for steering a steady line.
For one, he's bold enough to burst the popular myth of account manager Todd Beamer, whose "Let's roll!" was reclaimed into a facile, posthumous battle cry.
Greengrass calmly and correctly portrays Beamer as he was: just another hapless component of this rag-tag resistance. By refusing to single out individual acts of selflessness or 'leadership', he graces the memory of every passenger and crew member, equally.
But he also can't resist the urge to give us - and the families - something to cling to, in the face of all this panic and futility.
As a result, the counter-attack is overplayed, implying that the passengers managed to lynch two of the hijackers - contrary to the findings of the 9/11 Commission. On the ground, Greengrass slots hindsight-loaded words into the mouths of his out-of-control controllers ("We're at war with someone here!").
But United 93 is far from propaganda. With his flapping tin-pushers and yapping generals, Greengrass waves away the conspiracy theorists.
The United States Of America, the most powerful nation on Earth, was rendered impotent by incompetence, and it was left to a small group of people to unknowingly fight for its honour as they were fighting for their lives.
United 93 isn't a story about heroes or, as Pennsylvania governor Tom Ridge absurdly put it, "citizen soldiers". The passengers' actions weren't sacrificial. They weren't doing it out of patriotic nobility; for the flag or their Commander-In-Chief. Nor to deny Bin Laden a poster image of a ruptured White House dome.
They were doing it for themselves, for each other; so that they might stay alive and see the people they loved again.
United 93 isn't a story about martyrs. Unlike the poor souls on American 11, American 77 and United 175, these people were fully armed with the knowledge of what was going to happen to them.
They were given a chance to survive and, instead of clenching for nothingness, they rose up and refused to go quietly: one of the few nuggets of consolation glinting from the wreckage of that awful, awful day.
United 93 is an eloquent tribute to their fear and fury.