Kelly flew combat missions during the Gulf War. He was selected to become a NASA Space Shuttle pilot in 1996 and flew his first mission in 2001 as pilot of STS-108. He piloted STS-121 in 2006 and commanded STS-124 in 2008 and STS-134 in 2011. STS-134 was his final mission and the final mission of Space Shuttle "Endeavour".