Space Shuttle orbiter its maiden flight in 1977. An unpowered glider, it was carried by a modified Boeing 747 airliner called the Shuttle Carrier Aircraft and released for a series of atmospheric test flights and landings. "Enterprise" was partially disassembled and retired after completion of critical testing. The remaining orbiters were fully operational spacecraft, and were launched vertically as part of the Space Shuttle stack. "Columbia" was the first space-worthy orbiter, and made its inaugural flight in 1981. "Challenger", "Discovery", and "Atlantis" followed in 1983, 1984 and 1985 respectively. In 1986, "Challenger" was destroyed in an accident shortly after launch. "Endeavour" was built
Space Shuttle Columbia disaster crew of two. Less than a year after the accident, President Bush announced the Vision for Space Exploration, calling for the space shuttle fleet to complete the ISS, with retirement by the year 2010 following the completion of the ISS, to be replaced by a newly developed Crew Exploration Vehicle for travel to the Moon and Mars. NASA planned to return the space shuttle to service around September 2004; that date was pushed back to July 2005. On July 26, 2005, at 10:39 am EST, Space Shuttle "Discovery" cleared the tower on the "Return to Flight" mission STS-114, marking the