Audience members watch the United States Air Force Band Singing Sergeants during a flash mob at the Smithsonian National Air and Space Museum Udvar-Hazy Center in Chantilly, Va., Dec. 2, 2014. The Udvar-Hazy Center is home to thousands of aviation and space artifacts and is the companion facility to the Museum on the National Mall in Washington, DC. (U.S. Air Force photo/ Senior Airman Nesha Humes)