A SpaceX capsule delivered four astronauts to the International Space Station early Sunday in a NASA crew-swap mission that will allow a pair of stuck astronauts to return home after nine months on the orbiting lab.

Reaching orbit from NASA’s Kennedy Space Center, the newest crew includes NASA’s Anne McClain and Nichole Ayers, both military pilots; and Japan’s Takuya Onishi and Russia’s Kirill Peskov, both former airline pilots. They will spend the next six months at the space station, considered the normal stint, after springing Wilmore and Williams free.