El Al also has armed "Sky Marshals" who WILL shoot you on most, if not all air craft. their planes are also equiped with flare dispensers and other counter measures.
TAB is dead right about the menace to refineries, while I lived in Ca. 2 of the 5 area refineries were down for repairs, when a third had an explosion that killed some maintenance workers it was forced to close for repairs. I don't know what the effect was nation wide but locally gas prices nearly doubled.
as for protecting against terrorist attacks, forget it, it can not be done, the best you can hope for is to complicate their planning to the point it is not worth it. however, suicide bombers are not concerned with escape so that eliminates half their problems.
As others have mentioned, if all your defenses are up front as TSA has theirs set up, even if they ARE to stupid to make their approach through the employee angle, you have still assembled a large tempting target for them, people still remember the Lod air port massacre after nearly 40 years. And yes, news reports are the terrorists friend as front page stories with photo's of torn and bleeding bodies stay in the memories of people who may find themselves in the same situation (standing in the Check in line during rush hour) 2 people stabbed on page one has terror value than a vaporized city covered as a 1 inch blurb on page 37B.