What we are trying to stop has shifted from someone hijacking the plane to someone trying to blow it up. However, this is not a new threat at all, and there are always more ways of getting a bomb on the plane as well as more targets.
Perhaps, but why do we still focus then so much on 'hijacking' items, like knitting needles that would do little good in making bombs? We haven't reverted to pre 9/11 search coverage of hijack items. Actually, we haven't backed down at all on anything.
It seems that once something is identified a threat, it will always now be seen as a threat.
