When a ship carrier aircraft, you call it an aircraft carrier; and when an aircraft carries space shuttles? Yes, a shuttle carrier aircraft (SCA). In picture is the Atlantis riding piggyback on the NASA 911. The NASA's SCAs are two modified Boeing 747 jets. The SCAs are used to ferry shuttles back to the Kennedy Space Center from landing sites too distant for ground transport. The SCA-shuttle combo burns 100 litres of fuel per kilometre and can fly non-stop for 1,900 km. Each transcontinental trip costs about $1.7 million and its ground handling crew alone is 170-strong!