DENVER -- Friends and family members of Colorado pilot Jason Dahl said that it was difficult to listen to parts of the terrifying struggle captured on tape as Flight 93 was hijacked over Pennsylvania Sept. 11.

Flight attendants gathered at a Denver hotel restaurant Thursday night to honor their United and American Airlines co-workers who were lost in all four plane crashes Sept. 11.

Money raised at the event will go to the families of the 25 flight attendants who died in the terrorist hijackings.

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Hear The United Flight 93 Hijacking Tape

For the people who knew Dahl (pictured, right) and the other crewmembers of flight 93, the tapes of the cockpit confrontation were chilling.

"Actually just hearing it was really hard. I didn't know I was going to have that reaction, hearing them scream and stuff like that," United flight attendant Sandy Neil said.

Dahl's brother-in-law in California said that he believes it's Dahl's voice telling the hijackers to get out of the cockpit.

"Hearing the voice, I think it just triggers the enormity of the loss," brother-in-law Bill Heiderich said.

"It sounds exactly like something Jason would say. I think he actually believed if he said, 'Get out of my cockpit,' that someone would do it," he said.

The hijackers didn't get out, though, and soon they were pretending to be the flight crew.

"Ladies and gentlemen here it's the captain, please sit down. Keep remaining sitting. We have a bomb on board," one hijacker told the passengers.

"It makes me realize too, as a flight attendant, and a crewmember, they did everything possible to try to inhibit what was about to happen," United flight attendant Susan Hudson said.