Isn't the problem with airport security really that it never or rarely catches anyone and it is still pretty easily circumvented if you really wanted to.
Most terrorist are not just people that gets a sudden impulse to blow a plan up. They are people who plan it carefully and will certainly find a way to get around the security systems that are in place today.
You can take a look at the scenario presented here
http://boardingarea.com/blogs/flyin...s-one-with-a-rectal-bomb…-this-is-not-a-typo/ to me it sounds like a plausible scenario and something that could be done.
The only thing that you do with airport security today is to harass a lot of law abiding citizen just so that some can get the illusion of safety. I will not be the one to judge if that is a good trade off (I believe Ben Franklin already said something about this a long time ago), but if the terrorists aim is to hurt us where it really hurts, namely on the wallet, then they are succeeding. We are spending more money and time (and time is money, right) on airport security than we have ever done before.
I have heard some say that airport security is not there catch terrorist, but to prevent them from trying, that always reminds of the following joke.
Psychiatrist: Why do you keep whistling all the time?
Patient: To keep the tigers away.
Psychiatrist: We are in Denver, Colorado there are no tigers for thousands of miles.
Patient: See how well it works.