Film-maker Paul Greengrass attempts to deal with the many questions thrown up by 9/11 in his film about the final hijacking of that dreadful day. But he's the first to admit he has no answers, he tells Steve Pratt.

IT'S the question that film-maker Paul Greengrass has grown accustomed to as his 9/11 movie United 93 is released in cinemas. "Is it too soon?," he's asked about the Hollywood-backed movie centred around events on the fourth hijacked plane.

"I always say I understand the question, but I've never been asked it by a family of 9/11," he says.

"I've had many of them say, 'why did it take so long?'. It goes to the same issue. We had this vague feeling going into it, 'is this the right time, is it too soon?', but what we're really asking is, 'is it too soon for us?'.

"The truth is when these events happen, whether it's 9/11 or Omagh, we pause for a moment. We're not touched directly by them. We see the families, we feel sorry for them, we see them as victims.

"And then, frankly, we want them to go away because we want to get on with the rest of our lives. We want to wait for the World Cup, go to the pub, prepare for our summer holidays. We want our lives unchanged and you can see that in the response to 7/7.

"But if you're a family whose lives have been destroyed, changed forever irrevocably, you rage against that. You demand to be heard and that we, untouched by it, address the core questions: why has this happened and what are we going to do?".

United 93 is one of several Hollywood films being made about 9/11. A TV movie Flight 93 was premiered in January and Oliver Stone's film World Trade Centre, which opens later this year, stars Nicolas Cage as a police officer trapped in the rubble of the collapsed towers.

They'll be hard pressed to top Greengrass's brilliant and unsettling film, which plays like a thriller with the awful knowledge that it's for real and the thought playing at the back of your mind that there's no happy ending. Greengrass is well versed in tackling controversial subjects in documentary-style features. His most recent was Bloody Sunday, about the 1972 civil rights march in Northern Ireland that left 13 dead. Other credits include Omagh and The Murder Of Stephen Lawrence. He also co-wrote Spycatcher with Peter Wright.

For United 93, he recreated events on the doomed plane through interviews with the families of the 40 passengers and crew, members of the 9/11 commission, flight controllers, military and civilian personnel as well as flight recordings, public record and historical fact for the screenplay.

For him, those aboard United Airlines Flight 93 became the first citizens of the new world created in the aftermath of the Twin Towers terrorist attack. That's why he was interested in telling the story of the fourth plane, in which passengers fought back against the hijackers.

"It was the last plane that took off, because it took off late by chance because of air traffic delays," he says. "It always seemed to me that those 40 passengers were the first people to inhabit our world - the world of 'what are we going to do, what can we do and what will be the consequences of what we do?' "By the time of that hijack, 9/11 was basically all over. The Twin Towers had been hit half-an-hour before, the Pentagon was being hit as they were being hijacked. It was all over."

Keeping a balance between the families' sensibilities and telling the true story always creates a tension, as much in United 93 as in Bloody Sunday, Omagh and Stephen Lawrence. "What I feel is you have to see that involvement as central to what you're doing rather than a thing you've got to get around," he says.

"I've said it many times before when I've made films in Northern Ireland: if you want to understand some of the deeper truths around political violence, go and talk to people whose lives have been destroyed by it. That's when you really get to the heart of it.

"If you spend time with the Bloody Sunday families or the United 93 families, the extraordinary thing is you find very little thirst for revenge. What you do find is a great wide variety of opinions because with these events, these tragedies and atrocities, it's always disparate people united by this common event.

"They're linked by the really deep engagement that they inevitably have, with the core questions that lie at the heart of our response to political violence - why has this happened and what are we going to do?."

He clearly thinks the British response - "pathetic, pitiful" are his words - to 7/7 lags behind the US reaction to the terrible events of 2001, when the 9/11 commission established a central foundation stone for making decisions about what to do about the situation.

"The narrative of events of 7/7 is a shameful, shameful document. It's like Lord Widgery's account of Bloody Sunday. We sit here as a society and slumber through these events and if you're a victim of 7/7, you rage at it. So this 'too soon' thing is about us. We have a massive problem here and it's not easy. I don't have any of the answers, that's not my job."

He acknowledges there are American directors who'll make films about 9/11, but what was important for him was that he'd made these kinds of films before, in terms of the Irish Troubles, and that his early background was in ITV's World In Action.

"I'd spent a lot of time in my twenties going to places where bad stuff happens, bloodshed and conflict. It kind of marks you. You just get to feel like you know your way around those things. That was more important than that I was British.

"But, having said that, I did bring the actors to Britain. That was because I wanted them out of America to be in a single place and create this company feel and consider the story freed from any outside factors."

Certainly the success of hit thriller The Bourne Supremacy with Matt Damon gave him the clout to make the film on his own terms in this country, at Pinewood studios.

Making United 93 was an "amazing experience", something directors often say but he really means it.

Making films can be a bit thankless sometimes, he feels, but other times - and this was one of them - you go into work and remember why you love the job. At Pinewood, he gathered together with 120 people, many of them working actors but also air traffic controllers, military people and flight attendants who'd been involved on the day.

He concedes that no one can know exactly what happened when some of the passengers decided to try to overpower the hijackers and retake control of the plane. "People always ask, 'did you make it up?'. That's not how it is. You sit there with this range of opinion. Actors don't make things up, they're incredibly skilful at unlocking believable truths," he explains.

"You're sitting on a real aeroplane as we did in Pinewood. The mythology of United 93 is that they pushed the trolley down the aisle - it could never have happened. I can't prove to you that it didn't happen like that, but I know for sure it didn't.

"You sit there and try to make a thousand judgements like that. You end up with a film and say, 'it's our version of it'. But I believe, and I know that every person involved in that film from all the wide spectrum of professional opinions, believes it must have been something very like that."

* United 93 (15) opens in cinemas on June 2.