In case anyone missed CBS's "60 Minutes" yesterday (March 30, 2003), here's a link to the story...
Perhaps this explains (at least partially) the fervor of some airport operating authorities and airport police units in patrolling the airport's perimeter (the only thing they can "control" juristiction-wise), even though the threat envelope created by the missles extends much further out. Since these missiles could easily and quickly be pulled out of a car trunk and fired, one can see why the airport folks are leaning towards making the airport perimeter an exclusion zone, and just trying to keep -everyone- (including spotters) away. Even though the threat area is huge, the airport folks don't (understandably) want it happening from the area that they're responsible for.
The US Congresscritter quoted has a good point as far as the estimated $10 billion cost to outfit the domestic fleet with countermeasures, i.e. that a successful missile attack (absent countermeasures) could quickly create $10 billion in losses (and more) via an economic shutdown.