Security measures -- Terrorism -- 3 Prevention 2 Security measures 2 Aeronautics, Commercial -- 1 Airports -- 1 Business -- 1 more ... Business enterprises -- 1 Civil defense 1 Civil defense -- 1 Defenses 1 Economic aspects 1 Effect of terrorism on 1 Harbors -- 1 Hijacking of aircraft -- 1 Industries -- 1 Merchant marine -- 1 National security 1 National security -- 1 Passenger traffic 1 Politics and government -- 1 Prevention. -- 1 War on Terrorism, 2001-2009 1 less ...