People line up for security check at the Ronald Reagon National Airport outside Washington D.C., capital of the United States, Nov. 21, 2012. Travelers are flooding the nation's transportation system for the Thanksgiving holidays. (Xinhua/Zhang Jun)

An old lady dozes as travelers arrive at the Ronald Reagon National Airport outside Washington D.C., capital of the United States, Nov. 21, 2012. Travelers are flooding the nation's transportation system for the Thanksgiving holidays. (Xinhua/Zhang Jun)

People line up for security check at the Ronald Reagon National Airport outside Washington D.C., capital of the United States, Nov. 21, 2012. Travelers are flooding the nation's transportation system for the Thanksgiving holidays. (Xinhua/Zhang Jun)

People line up for security check at the Ronald Reagon National Airport outside Washington D.C., capital of the United States, Nov. 21, 2012. Travelers are flooding the nation's transportation system for the Thanksgiving holidays. (Xinhua/Zhang Jun)

People line up for security check at the Ronald Reagon National Airport outside Washington D.C., capital of the United States, Nov. 21, 2012. Travelers are flooding the nation's transportation system for the Thanksgiving holidays. (Xinhua/Zhang Jun)

People line up for security check at the Ronald Reagon National Airport outside Washington D.C., capital of the United States, Nov. 21, 2012. Travelers are flooding the nation's transportation system for the Thanksgiving holidays. (Xinhua/Zhang Jun)

People line up for security check at the Ronald Reagon National Airport outside Washington D.C., capital of the United States, Nov. 21, 2012. Travelers are flooding the nation's transportation system for the Thanksgiving holidays. (Xinhua/Zhang Jun)

People line up for security check at the Ronald Reagon National Airport outside Washington D.C., capital of the United States, Nov. 21, 2012. Travelers are flooding the nation's transportation system for the Thanksgiving holidays. (Xinhua/Zhang Jun)