Reviewed - United 93: United 93 is a powerfully visceral real-time drama from the director of Bloody Sunday, writes Michael Dwyer

BRITISH director Paul Greengrass, who received overdue international recognition with Bloody Sunday four years ago, imagines the unimaginable in United 93, which takes its title from the number of the plane that was hijacked on September 11th, 2001 and did not hit its target.

The available evidence - from the lovers, relatives and friends of passengers who contacted them inflight on their mobiles - is that the scheme for the plane to be the fourth weapon of mass destruction on that fatal day was thwarted when the passengers fought back. Another crucial factor was that the flight's delayed takeoff allowed time for the passengers to be alerted to the attacks on the World Trade Centre.

Greengrass treats the story with sensitivity through the form of a dramatised documentary that mixes unknown actors in an impressionistic collage of passengers and hijackers, along with real-life air traffic control staff as themselves. His film is one of those rare achievements, such as All the President's Men, which take material that is widely familiar and inject it with a dramatic urgency that is riveting, even though we know the ending from the beginning.

In what feels like a cruelly ominous scene, the camera prowls inside the empty plane before the crew come aboard. When the plane takes off on its scheduled journey from Newark to San Fransisco, the movie shifts into real time. Down on the ground at air traffic control, when the first plane hits the trade centre, we see it only as a blip on a radar screen, but we know what's coming. When the second plane strikes, the effect is devastating, no matter how many times we have seen the original footage.

As at least some of us felt when we watched that footage over and over again five years ago, the film places us in the position of voyeurs, but Greengrass eschews sensationalism and exploitation. Even the key line spoken by one passenger - "Let's roll," taken by Neil Young for a heartfelt song on the event - is muttered rather than delivered with the dramatic panache of a conventional Hollywood hero.

When the plane crashlands in Shanksville, Pennsylvania, as we know it will, those final five minutes of the film are terrifying, unbearable and stunning.