A: The simple answer: Nobody knows. There are anomalies in the passenger lists themselves, and many who supposedly died on the flights are not listed in the United States Death Registry.

Frankly, this particular question can't be answered without a valid determination of what hit the towers, the Pentagon and the field in Shanksville.  Were these passenger planes, military substitutes, or something else?  The question then devolves into whether you believe the government's story.  If you do, then you must ask yourself: (1) why they lied and said they didn't know it could happen despite their surveillance of the alleged hijackers for months before; (2) how they could produce names so soon after the event; and (3) why did they work so hard to prevent even a basic investigation into the purported crashes of four airliners -- the only airline crashes in American history that have never been investigated?

The people who made these decisions know who flew the planes (if anybody actually did), but you and I may never.  The suppression of evidence by the government is central to our unwillingness to believe what we have been told.  Under traditional rules of American jurisprudence, neither Osama bin Laden nor any Arab could ever be convicted of the 9/11 crimes, because no convincing proof that they did it has ever been presented.

As the planes wandered in the sky for over an hour, they passed over several airports and military bases.  Did they come down at any of these and were they swapped for other craft?  What did happen to the passengers?  No matter where they went, they are assumed to be dead.  If indeed they died, the issue of "wrongful death" (especially as our air-defense fighter jets seem NOT to have been deployed when necessary that day) becomes something Americans can pursue with their state legal representatives (District Attorneys, US Attorneys, State Attorney Generals).  Missing persons from the 9/11 planes were residents of many different states.  Your legal representatives have subpoena power in this kind of matter, and can charge individuals in the federal government with responsibility.