ANDREW CLARKE This is a film that is resolutely unHollywood. This is not a patriotic flag-waving movie for America seeking to restablish its self-esteem after the 9/11 attacks - it's not a tale of conventional heroism, of policemen and firefighters battling to save lives or make sense of the disaster happening around them.

ANDREW CLARKE

I am confidently predicting that come December 31 2006 United 93 will still be my film of the year. It has no big-name stars, no startling special effects, it is guaranteed to make you shed a tear and yet it is one of the most emotionally honest and rewarding films I have ever seen.

This is a film that is resolutely unHollywood. This is not a patriotic flag-waving movie for America seeking to restablish its self-esteem after the 9/11 attacks - it's not a tale of conventional heroism, of policemen and firefighters battling to save lives or make sense of the disaster happening around them.

Instead, it is a simple tale of a group of people, both on the ground and in the air, trying to understand what was happening to them on that fateful Tuesday morning.

United 93 - starring JJ Johnson, Ben Sliney, David Alan Basche, Gregg Henry, Christian Clemenson, Becky London, Trish Gates, Cheyenne Jackson and Chip Zien - tells what is believed to be the true story of the flight that was on its way to crash into the White House on September 11 2001 but was forced down by a passenger revolt into a field in Pennsylvania.

What gives the film its power is the fact is that it shot in an unsentimental documentary style. British director Paul Greengrass opts to use only handheld cameras, which effectively puts the audience in the same room with the characters. Nothing has been heightened for dramatic effect; the very ordinariness of the opening scenes gives the film its tremendous power to shock and move people to tears later on.

Greengrass tells the story from three points of view: that of the passengers, first at the airport departure lounge and then on the plane; from the air traffic control in New York, within sight of the Twin Towers; and from the control centre of a nearby military airbase.

Greengrass doesn't show anything that the people in these scenes didn't see or didn't know. We, the audience, are in the rooms with them. There are no close-up effects of planes hitting the towers on the Manhattan skyline, no galvanising speeches written with hindsight by Hollywood scriptwriters - this is getting on with the job even when the world is rapidly disintegrating around you.

Greengrass doesn't provide any information for his characters that wasn't available to them at the time. There's no mention of Osama bin Laden, nothing about Al Qaida, no mention of Muslims or terrorists from Afghanistan.

This film is designed to capture the idea of watching the event as it happened - complete with the bewilderment and confusion which reigned in New York air traffic control as aircraft disappeared from their screen and buried themselves first in the World Trade Centre and then in the Pentagon.

Make no mistake, this is a very emotionally powerful movie. It begs us to put ourselves in the position of the innocent passengers on flight United 93. What would we do if we were in their position?

Although, on the surface, it treads well-documented ground, it does provide well-researched, new information and gives an emotional but unsentimental focus to events happening on screen.

Greengrass wrote the screenplay based on exhaustive interviews with the passengers families and from information revealed by the official inquiry. Amazingly many of the passengers were able to phone their families while being held hostage and it was only then that they were informed about the hijacking of the planes that hit the World Trade Centre and then the Pentagon.

It was this information which provided the trigger for them to try and seize control of their own flight.

Among the new information that the inquiry brought to light was the fact that it was an incredibly busy day in the skies above New York. There were 4200 aircraft in the air at the time of the hijackings and United 93 spent 30 minutes in a queue on the taxi-way waiting for a take-off slot to become available.

Another amazing piece of information that came to light was that because of a US airforce exercise taking place that morning there were only four fighters available to protect the entire eastern seaboard and when they were scrambled permission was refused to enter New York space because of the density of the air traffic. There was simply nowhere for them to go without endangering themselves or the civilian aircraft.

The documentary style is further enhanced by the restrained nature of the dialogue - there's no battle cry when the passengers overwhelm their captors, they are just desperate people trying to avoid death.

The film is no less powerful because we know the outcome.

In fact, Greengrass cleverly uses minimalism to underline awfulness of their brave sacrifice by sticking to his guns and not showing an external shot of the plane hitting the ground and them dying in a spectacular fireball. Of course, they didn't see that.

Instead we get the view they got, from the cockpit trying to wrestle back control of the aircraft, we get the spiralling view of the ground getting closer and then blackness and silence.

This is not a comfortable to watch and yet, at the same time, it makes compelling viewing. You can't take your eyes off the screen, even when they are brimming with tears.

There's no false sentimentality, not a word or a sequence is out of place. It is an honest film which does its best to document a moment of incredible desperation by a group of ordinary people caught up in a situation they knew nothing about.

The use of the excellent unknown actors just adds to the documentary feel of the film.

Some commentators have asked why Greengrass didn't show the events from the hijackers' point of view - but that would have broken faith with the rest of the film, as the passengers and cabin crew themselves didn't know why the aircraft were being taken over.

The hijackers' story is another film entirely and probably a more speculative one as there is no-one left to provide the behind the scenes information.

The most powerful film of the year - please do go and see it.