I find it strange that people keep saying that the grounding of the flight was needless, and 'nothing happened anyway'. Isn't that a good thing and surely the whole point? Intercepting and stopping a terrorist act is all about making sure nothing happens and that things go on as normal. As frustrating as the current security procedures are, the fact that so far, nothing has happened since september 11th is an indication that they are yealding results.
We will never know how many would be terrorists have walked away without checking in, when they saw that their chance if success was slight.