 Two modified Boeing 747s were used to fly the shuttles back to KSC when they landed at Edwards AFB.N911NA was retired on February 8, 2012 and is now a parts hulk for the Stratospheric Observatory for Infrared Astronomy.Beginning in September 2014, N911NA was loaned out to the Joe Davies Heritage Airpark, in Palmdale, CA, where it is on outdoor display next to a B-52.