He was selected as an astronaut in 1996 and his first space shuttle flight was as the pilot of Endeavour in December 2001 to the International Space Station (ISS), which included the exchange of resident crews. He also piloted the space shuttle Discovery in July 2006, was commander of Discovery during its important mission of delivering a replacement part for the ISS’s malfunctioning toilet in May 2008, and was commander of the space shuttle Endeavour during its last flight in May 2011. He is the twin of the US astronaut Scott Kelly.