Suni Williams and Butch Wilmore were only supposed to be in space for about a week when they launched in June, but problems with their Boeing Starliner spacecraft extended their journey for months.

The crew-swap mission will enable NASA’s Butch Wilmore and Suni Williams to return to Earth from the International Space Station.

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