Americans Mostly Shrug Off Terror Warnings As Security Tightens at Nation's Airports, Bridges Dec. 22 — Travelers encountered tighter security at the nation's airports, train stations, bridges and highways Monday morning, a day after the government raised the national threat level and said attacks were possible during the holidays. On Sunday, the federal government raised the national terror-attack warning to "Code Orange," its second-highest level, following warnings that al-Qaida may be plotting attacks against the United States during the holidays. Homeland Security Secretary Tom Ridge said threat indicators are "perhaps greater now than at any point" since Sept. 11.