This Week in Photos, Week of April 13-19, 2012

Space Shuttle Discovery has its final flight, runners compete in the Boston Marathon, and celebrations mark the 100-day countdown to the start of the 2012 London Olympics.

Space Shuttle Discovery, mounted atop a 747 shuttle carrier aircraft, flies over the US Capitol on its final trip to retirement. The longest-serving orbiter in the space shuttle fleet was flown from Kennedy Space Center in Florida to the Washington, DC, area to be transferred to the Smithsonian National Air and Space Museum. It will be placed on display in the museum's Steven F. Udvar-Hazy Center.