Outside of deep intelligence circles no one truly knows the fates of the people who boarded the planes. My presumption is that the passengers were killed (gassed?) after having fulfilled their roles. Maybe, just maybe, the pilots were in on it and allowed to live. It would be pretty wild if one of the pilots were brought out on stage in a press conference.

Rumor is that none of the supposed hijackers boarded any of the planes. Some were purportedly spotted days after the big day.