Security measures Prevention 8 Terrorism -- 8 Aeronautics, Commercial -- 6 Hijacking of aircraft -- 4 Airports -- 3 Hijacking of aircraft 3 more ... Prevention. -- 3 Security measures -- 3 Terrorism 3 War on Terrorism, 2001-2009 3 Evaluation. -- 2 Government policy -- 2 Information warfare -- 2 National security -- 2 Air power -- 1 Astronautics and state -- 1 Asymmetric warfare 1 Buildings -- 1 Civil defense 1 Civil defense -- 1 Civilian use -- 1 Computer crimes 1 Computer networks -- 1 Cyberterrorism 1 Defenses 1 Diplomatic and consular service, American -- 1 Economic aspects 1 Embassy buildings -- 1 Embassy takeovers 1 less ...