Security measures Terrorism -- 5 Aeronautics, Commercial -- 3 Prevention 3 Prevention. -- 3 Security measures -- 3 War on Terrorism, 2001-2009 3 more ... Evaluation. -- 2 Government policy -- 2 National security -- 2 Air power -- 1 Airports -- 1 Astronautics and state -- 1 Buildings -- 1 Civil defense 1 Civil defense -- 1 Civilian use -- 1 Defenses 1 Diplomatic and consular service, American -- 1 Embassy buildings -- 1 Embassy takeovers 1 Exploration -- 1 Harbors -- 1 Hijacking of aircraft -- 1 History 1 History -- 1 Information warfare -- 1 Merchant marine -- 1 Military policy 1 National security 1 less ...