Recursive targets

Somebody mentions what occurred to me a few days ago: If it's the crowd that's the target, and not the plane, what happens if someone blows up the line at the security checkpoint? In the comments, someone else mentions the real doomsday scenario -- if you don't process people through the checkpoints quickly enough, then you always have a crowd, which means you always have a target, no matter how far upstream you move the checkpoint. About the only solution I can think of at that stage is the one we used on 9/12/2001 -- shut the system down.

Mind you, given the incidents we keep seeing in travel to and from the US (such as this one -- oh, yeah, Icelandic terrorists... now there's a threat...) I wouldn't be surprised if many in the administration consider such an outcome a feature, rather than a bug.