The space shuttle with the longest operational career was Discovery, measured from its first flight to its last. Discovery flew from August 30, 1984, through March 9, 2011, spanning more than 27 years.
Discovery’s first mission was STS-41-D, launched in 1984. Its final mission was STS-133, which delivered equipment and the Leonardo permanent multipurpose module to the International Space Station. By retirement, Discovery had completed 39 missions, more than any other shuttle orbiter.
The wording refers to calendar time between first and last flight, not total time in orbit or the number of missions. Columbia flew first, in 1981, but was lost in 2003. Atlantis began flying in 1985 and completed the program’s final mission in 2011, while Endeavour’s career ran from 1992 to 2011. None matched Discovery’s span.
Discovery also flew both post-accident return-to-flight missions: STS-26 after Challenger and STS-114 after Columbia. Its missions included launching and servicing the Hubble Space Telescope, supporting the International Space Station, and carrying John Glenn back into orbit in 1998.