Commercial airlines remain a target of terrorists,
Homeland Security Secretary Janet Napolitano said. She said items found at Osama bin Laden's compound indicate that the U.S. should maintain strict safety measures, and she noted that shoe bombs remain a threat. Napolitano also said the U.S. must balance the needs of travelers against the threat of an attack. "One tragic event in one part of the world can have a ripple effect across the entire travel and tourism sector," she said.