At the Shuttle Landing Facility at NASA’s Kennedy Space Center in Florida, workers secure a sling to space shuttle Discovery to enable the mate-demate device to lift it onto a Shuttle Carrier Aircraft. The device, known as the MDD, is a large gantry-like steel structure used to hoist a shuttle off the ground and position it onto the back of the aircraft, or SCA. The SCA is a Boeing 747 jet, originally manufactured for commercial use, which was modified by NASA to transport the shuttles between destinations on Earth. NASA 905 is scheduled to ferry Discovery to the Washington Dulles International Airport in Virginia on April 17, after which the shuttle will be placed on display in the Smithsonian's National Air and Space Museum Steven F. Udvar-Hazy Center.