CAPE CANAVERAL, Fla. - Space shuttle Discovery, mounted atop the Shuttle Carrier Aircraft, taxies down the runway at NASA's Kennedy Space Center in Florida. The duo departed Kennedy' s runway 15 at 7 a.m. EDT. The aircraft, known as an SCA, is a Boeing 747 jet, originally manufactured for commercial use, which was modified by NASA to transport the shuttles between destinations on Earth. This SCA, designated NASA 905, is assigned to the remaining ferry missions, delivering the shuttles to their permanent public display sites. NASA 905 carried 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 in Chantilly, Va. For more information on the SCA, visit http://www.nasa.gov/centers/dryden/news/FactSheets/FS- 013-DFRC.html. For more information on shuttle transition and retirement activities, visit http://www .nasa.gov/transition. Photo credit: NASA/Rusty Backer KSC-2012-2480