Space Shuttle Columbia that remained fitted to the avionics suite, and an internal airlock that, originally fitted into the other orbiters, was later removed in favor of an external airlock to facilitate Shuttle/Mir and Shuttle/International Space Station dockings. Due to its weight, "Columbia" could not have used the planned Centaur-G booster (cancelled after the loss of "Challenger"). The retention of the internal airlock allowed NASA to use "Columbia" for the STS-109 Hubble Space Telescope servicing mission, along with the Spacehab double module used on STS-107. Due to "Columbia's" heavier weight, it was less ideal for NASA to use it for missions to the
Space Shuttle Atlantis with Space Shuttle "Atlantis" over the course of its 33 missions. Because the shuttle sometimes flew crew members arriving and departing Mir and the ISS, not all of them launched and landed on "Atlantis". Astronaut Clayton Anderson, ESA astronaut Leopold Eyharts and Russian cosmonauts Nikolai Budarin and Anatoly Solovyev only launched on "Atlantis". Similarly, astronauts Daniel Tani and Sunita Williams, as well as cosmonauts Vladimir Dezhurov and Gennady Strekalov only landed with "Atlantis". Only 146 men and women both launched and landed aboard "Atlantis". Some of those people flew with "Atlantis" more than once. Taking them into account, 203 total