Via Tyler Cowen, I found this wonderful BusinessWeek article about the cost (both in lives and money) of heightened airport security. Matt Yglesias responded here. The best part of his post is this pity sentence:
If commercial airplanes were no more secure than your average city bus, planes would be blown up as frequently as city buses—which is to say never.
Of course, a critic might point out that blowing up a plane is not the greatest fear. Under the 9/11 model, a plane has many benefits over a bus as a weapon — it is much more mobile than a bus, can hit targets that buses can’t and from more vulnerable angles, and packs a larger punch because of the enormous amount of jet fuel planes carry. Sure, many cockpits nowadays have secure, reinforced doors, but again a critic might be wary of the I’ll-kill-one-passenger-a-minute-until-you-open-that-door threat that was parodied in the slapstick comedy Passanger 57. Wait, that wasn’t a comedy? And then again in Air Force One, and probably again in a hundred other bad ’90s action films.
However, it’s important to note that under a model of zero percent airport security the Air Marshal program could be drastically expanded to basically insure that every major commercial flight had a marshal onboard. I think that’s overkill, but it could squelch fears of a 9/11-style repeat. I’m also curious, though, about evasive action by the pilots. It seems like a significant roll and pitch back and forth a few times could basically disarm any passenger with a weapon before they even knew what was happening. Presumably anyone standing at the time would suffer significant injuries, but it seems like this would be a simple, second-best option that could immediately be followed by an emergency landing. Also, to take over a plane you basically have to ensure you are standing and mobile while everyone else is seated as to suppress resistance, which makes this method doubly effective and likely to minimize non-combatant injuries.