Talking about aviation only (with full respect for the victims of terrorist attacks)....
I think that the very hard times are in front of all american airliners, specially the bigger ones.
It's obvious that the whole attack was made by some very well organized terrorist group. If we supose that the bad guys will be found and captured, do you think that that solves the whole problem? There is also a solution of wiping all the possible terrorists from the face of earth, which is impossible.
After all that happened, the threat will be the same. USA will remain the target, specially US airliners.
Who will fly them? Airline security (and airport security) failed the test. The great plans once introduced by PanAm in late 80's, by ex president Ford, never lived. Passenger screening and profiling was never introduced in the right way, and all the budget for that was used to cover PanAm's losses in pax transport.
Maybe now it's time for the all american airliners to introduce that kind of system back again. They should take more care when hiring the security staff, and passengers should not be bodered with "tough" security measures, because it there for their own safety.
Still, there will be years before people will seat in american airliner with smile on their face.
Which one will dissapear? Maybe most of them?