The 2,500 mourners clutched each other and wept as people who lost their spouses described their families and the connection they felt to Cantor Fitzgerald.

"The company was made up of a lot of people like my husband ambitious, aggressive and successful people who were all in the prime of their lives," said Joan Kirwin, whose husband, Glenn Kirwin, 40, was a partner with the firm.

On large poster boards, organisers posted photographs of the dead and missing, and friends and family wrote messages.

One child wrote to her father: "Thank you for playing caveman ... and for letting me have dessert even when I didn't eat dinner."

The firm's chief executive, Howard Lutnick, wept while addressing the gathering. Lutnick's brother, Gary, is among those missing in the attack. Howard Lutnick said many people have asked him how he manages to go on.

"I tell you, it's a physical thing. I have received so many hugs and kisses from everybody here," Lutnick said. "Because when I feel you next to me, I feel the energy and you help me. Without those hugs, there's no chance that I could have gone on."

Mayor Rudolph Giuliani sat next to Lutnick during the service.

"There are many different kinds of heroism, and one of them is the quiet heroism of working hard, supporting a family and pursuing a dream," Giuliani said.