Spectators interact with The United States Air Force Band members after their flash mob performance at The Smithsonian's National Air and Space Museum, Washington, D.C., Dec. 3, 2013. The band surprised museum visitors by breaking out in holiday songs to spread the word about their free upcoming holiday concerts in the National Capitol Region. The National Air and Space Museum welcomes on average eight million people annually, making it the most visited museum complex in the country. (U.S. Air Force photo by/ Airman 1st Class Nesha Humes)