Terrorists like to stick with what they know. They know that a simple assault on an airline industry such as I described before would directly effect the airline industry to the tune of hundreds of milllions of dollars, that the riple effect likely climb into the billions of dollars nationally, and that the psychological effect would be, from their point of view, priceless. They also know, or should know if they are half the threat we believe them to be, they could pull it off with ease.
As for allocation of resources, depending on the airport, a handful of suicide pact shooters targeting TSA security personel and targets of opportunity would all but crash the industry. The cost? A handful of "soldiers" and their arms. Peanuts, from their point of view.
Now, pitted against that potential threat we have well intended LEOs toting pistols and batons from a variety of municiple, state, and to a limited extent federal entities. Are their shotguns and rifles locked away somewhere? Most likely. Do they do much good there? Debatably, no. Which is why we are debating.
Me, I'd like to see M4s or something similar on the shoulders of strategically placed officers. I imagine more than a few folks in Boston argued the same. But others argued against the idea, and a compromise was struck. So handy, not too terribly ominous looking, somewhat expensive but very well crafter SMGs were selected. A good compromise? Debatably, yes. Debatably, no. Which is why the debate will undoubtably continue...
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Not to suggest that any other imaginable scenarious are less likely, just that one will be hard pressed to attach the dollar figure associated with an airline industry related attack. (It isn't like nation wide attacks on bowling alleys would have the same impact.)