Space Shuttle landing at Edwards, the orbiter was flown back to the KSC on the Shuttle Carrier Aircraft, a specially modified Boeing 747. The first orbiter, "Enterprise", was built in 1976, used in Approach and Landing Tests and had no orbital capability. Four fully operational orbiters were initially built: "Columbia", "Challenger", "Discovery", and "Atlantis". Of these, two were lost in mission accidents: "Challenger" in 1986 and "Columbia" in 2003, with a total of fourteen astronauts killed. A fifth operational (and sixth in total) orbiter, "Endeavour", was built in 1991 to replace "Challenger". The Space Shuttle was retired from service upon the conclusion
Space Shuttle made Space Shuttle thermal protection system tiles available to schools and universities for less than US$25 each. About 7,000 tiles were available on a first-come, first-served basis, limited to one per institution. On April 12, 2011, NASA announced selection of locations for the remaining Shuttle orbiters: In August 2011, the NASA Office of Inspector General (OIG) published a "Review of NASA's Selection of Display Locations for the Space Shuttle Orbiters"; the review had four main findings: The NASA OIG had three recommendations, saying NASA should: In September 2011, the CEO and two board members of Seattle's Museum of Flight met