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.

SpaceX launched the rescue mission on Saturday with a downsized crew of two astronauts and two empty seats reserved for Butch Wilmore and Suni Williams, who will return next year. The Dragon capsule docked in darkness as the two craft soared 265 miles (426 kilometers) above Botswana.

After multiple delays, NASA’s SpaceX Crew-9 mission finally launched two astronauts into space on Saturday from Cape Canaveral.The mission took off at 1:17 p.m. on a SpaceX Crew Dragon spacecraft, carrying NASA astronauts Nick Hague and Roscosmos cosmonaut Aleksandr Gorbunov to the International Space Station.