Space Shuttle gliding and landing; it was originally intended to be outfitted for orbital operations after the test program, but it was found more economical to upgrade the structural test article STA-099 into orbiter "Challenger" (OV-099). An additional test article, dubbed "Pathfinder" (OV-098), was built for form and fit tests, and is on display at the Alabama Space and Rocket Center in Huntsville, AL. "Challenger" disintegrated 73 seconds after launch in 1986, and "Endeavour" was built as a replacement from structural spare components. Building "Endeavour" cost about US$1.7 billion. "Columbia" broke apart over Texas during re-entry in 2003. A Space Shuttle launch
Teacher in Space Project teachers into space. The new Teachers in Space program began in 2005. In March 2005, Teacher in Space candidate Pam Leestma, a second-grade teacher and cousin of Space Shuttle astronaut David Leestma, completed a training flight aboard a MiG-21 operated by X-Rocket, LLC. Armadillo Aerospace, Masten Space Systems, PlanetSpace, Rocketplane Limited, Inc., and XCOR Aerospace pledged flights to the new Teachers in Space project. Advisors to the new Teachers in Space project include SpaceShipOne builder and Ansari X-Prize winner Burt Rutan, X-Prize founder Peter Diamandis, Apollo astronaut Buzz Aldrin, and private astronaut and X-Prize sponsor Anousheh Ansari. The United States