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