The Space Shuttle Discovery has more spaceflights than any other spacecraft to date. Quoting from the Wikipedia article entitled, "Space Shuttle Discovery,"
Discovery became the third operational orbiter to enter service, preceded by Columbia and Challenger. It embarked on its last mission, STS-133, on February 24, 2011 and touched down for the final time at Kennedy Space Center on March 9, having spent a cumulative total of almost a full year in space. Discovery performed both research and International Space Station (ISS) assembly missions. It also carried the Hubble Space Telescope into orbit. Discovery was the first operational shuttle to be retired, followed by Endeavour and then Atlantis.The Space Shuttle Discovery is housed in the Smithsonian National Air and Space Museum, Steven F. Udvar-Hazy Center in Chantilly, Virginia. By the way, it is really huge compared to almost all the other airplanes or spacecraft housed in the museum.