The studio behind 9/11 film United 93 is standing by the film's trailer, despite audience complaints.
United 93 is directed by British film-maker Paul Greengrass
The film focuses on the fourth hijacked plane which passengers attempted to retake from hijackers before it crashed in Pennsylvania on 11 September 2001.
"We expect that some moviegoers will have a strong response to its images and narrative," Universal Studios said in a statement.
A New York cinema has pulled the film's trailer after it upset viewers.
The trailer, which is being shown on about 3,000 screens across the US, contains documentary footage of the two planes hitting the World Trade Center twin towers in New York on 11 September 2001.
The AMC Loews Lincoln Square 12 cinema in Manhattan decided not to show the trailer after customers complained they found it distressing.
United Airlines flight 93 crashed in Shanksville, Pennsylvania
"I don't think people are ready for this," said manager Kevin Adjodha.
The film, which will be launched at New York's Tribeca film festival next month, gives a real-time account of the plane's hijack until its crash 90 minutes later.
Universal Studios believes the realistic nature of the trailer is necessary "so that those who elect to see the film will be prepared for the experience".
Director Paul Greengrass, whose films include The Bourne Supremacy and Bloody Sunday, worked closely with the bereaved families of victims of the United Airlines flight.
"We are very supportive of the film," said Tammie Rosen, publicist for the Tribeca film festival, where the film will debut on 25 April.
The film festival was set up by Robert De Niro to help revitalise Manhattan's economy in the wake of the terrorist attacks.
Families of the victims will see the film ahead of the premiere, while Universal Pictures has pledged to donate a proportion of the film's earnings to the Flight 93 National Memorial.