SAN FRANCISCO - AUGUST 10: A TSA employee searches the luggage of a United Airlines passenger at a security checkpoint at San Francisco International Airport August 10, 2006 in San Francisco, California. The Department of Homeland Security raised the terrorism alert to Red, the highest level, for commercial flights from Britain to the United States. The U.S. government banned all liquids and gels from flights effective immediately. (Photo by Justin Sullivan/Getty Images)
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