The U.S. government raised the security alert on passenger planes to its highest level for the first time on Thursday after Britain said it had foiled a plot to blow up flights to the United States. The U.S. Department of Homeland Security also barred passengers from carrying liquids, including beverages, hair gels and lotions, aboard planes. It said travelers in both countries should expect long delays. Homeland Security said it took an unprecedented step by raising the threat level for commercial flights originating in the United Kingdom to "severe," or red. The threat level for all other commercial aircraft operating in or destined for the United States would be raised to "high," or orange, from "elevated," or yellow, Homeland Security Secretary Michael Chertoff said in a statement. The threat level for the country as a whole remained at yellow, according to the department's Web site. A U.S. intelligence official said authorities believe the plot involved sophisticated liquid explosives that were to have been carried on to aircraft, with battery triggers possibly stored in alarm clocks, laptop computers and calculators. A British police source said the plot was believed to involve a "liquid chemical" device, according to a report of Reuters.
