Maybe this is maybe a little off-topic..... but the present high profile security, whilst highly knee-jerk (imho), will simply drive terrorism into more guaranteed, but lower risk (of being discovered in the execution of it), delivery mechanisms.
E.g. A determined Johnny Terrorist doesn't need to commandeer an airliner to do a lot of damage, especially so when a 'light' aircraft will do just as well.. .I.e. He / she fills the thing full of high-explosives, e.g. most light aircraft can lift at least 1000lbs of payload (and just what kind of damage could you do with 1000lb of Semtex ?), takes-off from some remote airfield (and there are plenty of them), flies as low and fast as possible, and then crashes it into the middle of, say, the Houses of Parliament during a debate, or Twickenham during an International, or a Man Utd home match...... I'm sure that you get the picture.
The IRA / ETA / etc, have been doing this sort of thing for years (with cars / trucks), albeit that they try hard not to martyr themselves in the process - which is not a problem our newest foe seems to worry about.
Indeed the above is almost so easy that I'm very surprised that its not been done it already, or perhaps JohnnyT is just waiting for their moment ?!
Ho hum........