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 of "Atlantis"s final flight on July 21, 2011. The U.S. has since relied primarily on the Russian Soyuz spacecraft to transport astronauts to the International Space Station. The Space Shuttle was a partially reusable human spaceflight vehicle capable of reaching low Earth orbit, commissioned and operated by the U.S. National Aeronautics and Space Administration (NASA) from 1981 to 2011. It resulted from shuttle design studies conducted by NASA and the U.S. Air Force in the 1960s and was first proposed for development as part of an ambitious second-generation Space Transportation System (STS) of space vehicles to follow the Apollo program