New York ? The first few hours of the Sept. 11 attacks have been imagined and replayed countless ways in the minds of many, but for the first time, a movie of that nightmare premiered on the big screen.

“United 93,” the first feature film to dramatize the Sept. 11, 2001, story, opened the Tribeca Film Festival on Tuesday in front of a somber audience that included Hollywood stars, city officials and victims’ relatives.

“The vision is something we see in our heads every day,” said Janice Snyder, whose daughter Christine was on the flight. “It’s time for this. The public needs to know, they need to remember and know what the families have gone through.”

The 90-minute movie takes place in real time and portrays the gripping story of the flight that left Newark, N.J., and crashed in a Pennsylvania field after passengers rallied against their hijackers and tried to recapture control of the jet.

At Tuesday’s premiere, the screen went dark after the stomach-turning sequence showing the plane’s nosedive. The theater was silent except for the gut-wrenching sobs and wails from the loge, where the relatives were seated together.

Moviegoers absorbed and shared their pain. Throughout the screening, they wept, drew sharp breaths, gasped and covered their faces with their hands. They shifted in their seats, sometimes to look back at the family section.

“You saw moviemaking and real life come together,” said Jeffrey Sachs, a consultant from Manhattan who attended the premiere. “It fills in the mystery of what happened.”

Flight 93 was the fourth plane hijacked that morning, crashing near Shanksville, Pa., minutes after the first trade center tower collapsed in lower Manhattan.

In this photo provided by Universal Studios, Becky London and Tom O'Rourke as Jean and Donald Peterson comfort one another aboard United Airlines Flight 93 in the unflinching drama 'United 93.'

In the film, the Flight 93 story is juxtaposed with that of the air traffic controllers, who watched with disbelief as four planes were seized and crashed by 19 terrorists. American Airlines Flight 11 slammed first into the north tower, United Airlines 175 hit the south tower and United 77 went down at the Pentagon.

Officials believe Flight 93, carrying 40 passengers and crew plus the four hijackers, was headed for the White House or the Capitol. The film uses that to suggest that the passenger uprising might have saved lives – a subtle bright spot amid the heartstopping devastation.

Relatives of people who were on Flight 93 collaborated with writer-director Paul Greengrass to lend authenticity to the characters and story of the movie, which opens nationwide Friday.

Greengrass did take some creative license – using what relatives told him about the victims’ personalities to envision what they might have done or which role they played in the revolt.

“Only 40 people truly know what happened that day and I thought he went to painstaking grounds to make it feel that all 40 of them were a part of it,” said Ken Nacke, whose brother Louis J. Nacke was killed.

Nacke said he found himself “rooting for them, for a different outcome.”

For some, seeing reminders of 9-11 on the big screen was too disturbing. A few theaters in the New York area pulled the film’s trailer this spring after moviegoers complained about the upsetting images.

Greengrass and film festival founders acknowledge that the film stirs powerful emotions but say the Tribeca gathering is appropriate for its world premiere. The festival, which runs through May 7, was created to help lower Manhattan recover economically from the 2001 attacks.

“Remembering is painful, it’s difficult, but it can be inspiring and it can give wisdom,” Greengrass told the audience before the film started.