The spacecraft commander sat on the left and, in addition to command duties, operated the spacecraft's flight controls. The Command Module pilot sat in the center, overseeing guidance and navigation and sometimes flying the spacecraft; on a lunar mission, that pilot stayed in the Command Module while the other two astronauts descended to the Moon's surface. The Lunar Module pilot sat on the right and was responsible for Command Module subsystems and for piloting the Lunar Module, the lander that guided astronauts to the Moon's surface. Although each astronaut had specific duties, they could take over one another's duties, and the Command Module was designed so one astronaut could return it safely to Earth.