Security measures Terrorism -- 5 Aeronautics, Commercial -- 3 Prevention. -- 3 War on Terrorism, 2001-2009 3 Evaluation. -- 2 Government policy -- 2 more ... National security -- 2 Prevention 2 Security measures -- 2 Air power -- 1 Airports -- 1 Civil defense 1 Civil defense -- 1 Defenses 1 Harbors -- 1 Hijacking of aircraft -- 1 Information warfare -- 1 Merchant marine -- 1 Military policy 1 National security 1 Passenger traffic 1 Politics and government -- 1 less ...