Two quick replies to Garett:

1. If terrorists were as flexible as he suggests, airport security would be useless.  Terrorists would simply switch to one of the countless undefended targets: trains, sporting events, malls, etc.  Profiling doesn’t have to be perfect to be extremely effective, and I don’t see that Garett’s counter-examples show otherwise.

Slightly different perspective: Right now, we use the profile, “Terrorists love targeting air travel.”  Given the paucity of U.S. soil attacks in the last eleven years, we can conclude that either (a) this profiling works well, or (b) there’s little threat to begin with.

2. The original issue was whether free-market airport security would be more convenient.  A more elegant way to make my original point: When security gives you an easy time, do you become (a) more reluctant to use that airport, because you’re afraid their lackadaisical attitude makes terrorism significantly more likely, or (b) less reluctant to use that airport, because you value convenience and aren’t seriously worried about terrorism? 

My sample could be biased, but everyone I’ve heard or overheard in the last ten years has reaction (b).  If you were running a profit-maximizing airport, wouldn’t (b) be the reaction you’d aim for?

Of course, if seemingly asinine airport security measures are really saving lots of lives from terrorist attacks, there’s a big offsetting factor: making life convenient for passengers today risks massive negative publicity and low ticket sales tomorrow.  Yet insofar as airport security is basically just security theater, you should conclude, contra Garett, that free-market security would be markedly more convenient for (most) air travelers.