Space shuttle Discovery makes final flight

In this photo provided by NASA, Space Shuttle Discovery, mounted on the Shuttle Carrier Aircraft lands at Washington Dulles International Airport, Tuesday, April 17, 2012, in Sterling, Va. Discovery is en route from Kennedy Space Center to the Smithsonian National Air and Space Museum Udvar/Hazy Center at Dulles International Airport. The oldest surviving shuttle, Discovery holds the all-time record with 39 missions, 148 million miles, 5,830 orbits of Earth, and 365 days spent in space. All that was achieved in under 27 years.(AP Photo/NASA, Paul E. Alers)