I was never keen on the idea of air marshals & nothing I've seen has changed my mind about this. I'm not sure how much difference they make & it would be interesting to see some statistics. Not a lot in my view & they could even make things worse if it came to the crunch.
I also don't know the stats, although I've heard a few stories about air marshals effectively and safely dealing with the more typical disruptive passengers. I've heard of more cases where ordinary passengers, untrained and caught up in the heat of the moment, dealt with such passengers, often with needless injury and even death. But my opinion is based more on thinking how things might've shaken down differently on 9/11/01 had there been armed agents aboard those four flights. I can't see how they could've possibly made things worse in that situation. Even the outcome of the passenger uprising aboard Flight 93, which led to the loss of all aboard, was more favorable than the hijackers' planned outcome, which would've no doubt killed many more people. I think it's safe to assume those hijackers had the same intention as the other three teams: wreak as much death and destruction as possible. It is
extremely unlikely that any negotiation would've been possible, so what else could be done? It may have been dumb luck that Flight 93 came down in a sparsely-populated area, but... I dunno, I guess in light of what happened that day, I just think that putting up a fight is the choice that makes the most sense to me, to deny the hijackers the satisfaction, if nothing else. If it ever happens to me, I'll damn sure not sit there writing farewell notes- I'll fight.
Then there's the El Al safety record since they started putting armed security aboard every (?) flight- worth considering in assessing the need for such security. If I'm not mistaken, El Al's agents are not anonymous- makes for an unpleasant reminder of the random savagery of terrorism, but it also makes a damn good deterrent.