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.

Two astronauts stranded for more than nine months on the International Space Station (ISS) were a step closer to returning home on Sunday, after a replacement crew docked at the orbital outpost.

SpaceX launched a crewed NASA mission on Friday to return two astronauts from the International Space Station, after technical issues with Boeing’s spacecraft extended their stay for nine months, leading SpaceX CEO Elon Musk and President Donald Trump to suggest they were stranded for “political reasons.”