NASA has removed two astronauts from a forthcoming SpaceX mission to make room for two others needing a new ride home from space.

The SpaceX Crew-9 mission will now fly only NASA astronaut and U.S. Space Force commander Nick Hague, and Roscosmos astronaut and mission specialist Aleksandr Gorbunov to the International Space Station (ISS), NASA officials announced Friday (Aug. 30). This will leave two seats empty in the Crew Dragon to bring home NASA astronauts Butch Wilmore and Suni Williams, who are unable to return to Earth aboard Boeing Starliner as planned.

Original Crew-9 commander Zena Cardman and mission specialist Stephanie Wilson, a space shuttle astronaut, will sit this spaceflight out. But the NASA astronauts "are eligible for reassignment on a future mission," agency officials added in the statement. Hague was originally the pilot of Crew-9, but is now the commander; Gorbunov remains as mission specialist. 

Starliner is on a historic first test mission with astronauts and reached the ISS on June 6 after experiencing trouble with its propulsion system and thrusters. Following two months of tests and safety discussions, NASA eventually said the risk was unacceptable to return Wilmore and Williams home on Starliner due to uncertainties about how well the thrusters would work. (Starliner should undock uncrewed from the ISS on Sept. 6, to free up its docking port on the U.S. Harmony module for Crew-9.)

The agency considered several options for the Starliner's astronauts' return before electing to launch Crew-9's spacecraft half-empty for an expected February 2025 mission conclusion. This allows Crew-9 a normal half-year ISS rotation and will bring home the Starliner astronauts after roughly eight months in space; the Crew-9 mission was delayed from an initial Aug. 18 launch date to make the necessary changes.