Because NASA rotates space station crews approximately every six months, this newly launched flight with two empty seats reserved for Wilmore and Williams won’t return until late February. Officials said there wasn’t a way to bring them back earlier on SpaceX without interrupting other scheduled missions.

NASA astronaut Nick Hague and Roscosmos cosmonaut Aleksandr Gorbunov boarded the ISS shortly after the Dragon capsule docked at the station at 2130 GMT, NASA said in a post on X. The SpaceX Crew-9 mission was supposed to transport four astronauts to the ISS until two empty seats had to be opened up for Wilmore and Williams after the Boeing Starliner capsule they arrived on in June was deemed unfit to return them to Earth.

The U.S. Federal Aviation Administration is requiring an investigation of the anomaly a SpaceX Falcon 9 rocket experienced during the Crew-9 astronaut launch on Sept. 28.

The SpaceX Dragon, selected by NASA to transport astronauts Suni Williams and Butch Wilmore home, arrived Sunday at the International Space Station.

The Dragon capsule has two empty seats for Butch Wilmore and Suni Williams, who were only meant to be on the ISS for eight days, but were forced to remain there because of a fault discovered during the flight.

SpaceX launched the rescue mission on Saturday with two seats reserved for Butch Wilmore and Suni Williams, who will return to Earth in 2025.

After their weeklong journey turned into a monthslong stay on the International Space Station, two Boeing Starliner astronauts are now within reach of the spacecraft that will eventually bring them home.