The week's best photos

This handout photo provided by NASA shows the Space shuttle Discovery, mounted atop a NASA 747 Shuttle Carrier Aircraft, flying over Washington skyline, including the Washington Monument, as seen from a NASA T-38 aircraft, Tuesday, April 17, 2012. Discovery, the longest-serving orbiter will be placed to its new home, the Smithsonian's National Air and Space Museum's Steven F. Udvar-Hazy Center in Chantilly, Va. (AP Photo/NASA, Robert Markowitz)