The Tribeca film festival, founded by Robert De Niro, has opened with the world premiere of a movie about the 11 September terrorist attacks.
Opening film United 93 dramatises the events of 11 September 2001
United 93 is set on the plane which crashed in Pennsylvania after its passengers fought with hijackers.
De Niro, who created the festival to help revitalise lower Manhattan after the events of 2001, said "it would seem strange" not to show the movie.
Several of the festival's 275 films also tackle the impact of that day.
These include documentaries about a fire department chaplain killed at the World Trade Center - entitled Saint of 9/11 -
and also The Heart of Steel, about volunteers who helped victims of the attacks.
Festival creator Robert De Niro said it was right to show United 93
Writer-director Paul Greengrass, who made United 93, said Tribeca was "the most appropriate place for the film to play first".
He added it was "an honour and a privilege to bring this film there. It's daunting and it's humbling, but I know in my heart we all did our best to honour this subject".
De Niro acknowledged that "some will be ready, and some will not be ready" for United 93.
"Not everyone is going to feel good, of course. But after four and a half years, it feels like the right thing to do," he said.
A remake of disaster movie Poseidon is among the premieres
Some cinemas in the US have already pulled trailers for United 93 after audiences became upset.
Among the 90 premieres at the festival is the first US screening of Mission: Impossible 3, which sees Tom Cruise travelling across Manhattan by helicopter, speedboat, sports car and underground train.
Other major movies include the disaster remake Poseidon, with Kurt Russell and Josh Lucas, and Lonely Hearts, which stars John Travolta and James Gandolfini as detectives tracking down two killers.
More than 4,000 productions were submitted for consideration by the organisers of the two-week festival.