He trained for a six-month mission to the International Space Station and was launched on the Space Shuttle Discovery STS-121 mission to join Expedition 13. The launch date was set for 1 July 2006, but was moved to 2 July, and finally launched on 4 July 2006 due to weather delays. Discovery departed 15 July, leaving Reiter behind with Expedition 13. He later became part of Expedition 14 before returning to Earth aboard Discovery during the STS-116 mission.