His four space shuttle flights include the Atlantis mission in September 1996 that docked with the Russian space station Mir. He flew on Endeavour to the International Space Station as a member of the fourth resident crew. His 196 days there set the US endurance record in space, along with fellow crew member Daniel Bursch. He has logged 231 days in space and is now serving in the Office of Space Science at NASA's headquarters in Washington, DC. Walz was selected as an astronaut in 1990 and left NASA in 2008.