STS-133 (ISS assembly flight ULF5) was the 133rd mission in NASA's Space Shuttle program; during the mission, Space Shuttle Discovery docked with the International Space Station. It was Discovery's 39th and final mission. The mission launched on 24 February 2011, and landed on 9 March 2011. The crew consisted of six American astronauts, all of whom had been on prior spaceflights, headed by Commander Steven Lindsey.