Snaga II, I think you'll find that Air Force One has some pretty smart defence systems.
HD, what do you propose? Police to make regular house to house searches? Ban the sale of such equipment in the UK? Fine, they'll go and buy them in the USA (and elsewhere). And do you really believe that terrorist plans will rely on spotters' information? I think not.
The reality is that preventing enthusiasts from using said equipment will not improve security against terrorism one iota. Total waste of time and just about as effective as the latest 'booze asbos'.