The purpose of art is to be the radar of a culture

Francis Ford Coppola

But despite the initial shock of the attacks, Hollywood has slipped back into its old way of thinking, he said.

"We were all hopeful that such an historical event would bring about films of greater content that tried to shed light on human contemporary life," he told BBC Bangkok Correspondent Jonathan Head.

"The purpose of art is to try to be the radar of a culture, so you hope films could be more helpful in showing things that would be more useful to people to try to understand how to live together.

"But my hunch is that things settled down to be more of the same."

After 11 September, a number of Hollywood directors said they thought film-making would never be able to tackle some subjects - like violence and terrorism - in the same way again.

Coppola was filming in New York on 11 September

Some film releases were postponed - but Collateral Damage, about a terrorist attack, and war films like Black Hawk Down have gone on to enjoy box office success.

And there is evidence to suggest that cinema-goers are looking for escapism more than ever, rather than being faced with serious issues.

Coppola put his own film on hold after the attacks - and has said he has only just worked out how it can carry on.

He was filming in New York when the attacks took place, and some parts of the film, Megalopolis, echoed the events of 11 September.

The film, which he describes as a "political fantasy", is about building a city of the future and featured an old Soviet satellite falling to earth and demolishing a part of New York.

Coppola has been working on a film in Thailand

"All of a sudden, something similar to what the story was about happened," he said.

"It took me a while to really scratch my head and think, well, how am I going to deal with this?

"I believe I've come up with a way to approach it now, but for a while I didn't know quite what I was going to do."

He has also been helping adapt the most expensive Thai film ever, Suriyothai, for an international audience.

The film was originally released in 2001 - but Coppola has been working with director Prince Chatri Chalerm Yukol to make it Asia's latest global hit, following the success of Crouching Tiger, Hidden Dragon.

He has described the film as a "fabulous epic" and has been filming new scenes and cutting others out.

"It's an incredible story of the evolution of a nation, [with] very memorable characters and some plot line aspects that are very arresting and moving," he said.