Question: why did nasa shut down the space shuttle program

title: Space Shuttle retirement
text: 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 `` SOFIA '' 747 . 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 the B - 52 . The other aircraft , N905NA was used to send Discovery , Endeavour and Enterprise to their museums and in September 2012 was found to have few parts for Sofia . It is currently a museum piece at the Johnson Space Center . NASA