SpaceX’s Crew-9 mission will launch to the International Space Station with only NASA’s Nick Hague and Roscosmos’ Aleksandr Gorbunov onboard, according to an update on Friday. Crew-9 will launch “no earlier” than September 24th, with plans to bring delayed Starliner astronauts Barry Wilmore and Sunita Williams back to Earth next February.

NASA says the other two US astronauts initially chosen for the mission, Zena Cardman and Stephanie Wilson, will be eligible for reassignment. The agency doesn’t specify why it split the crew up. Despite serving as a ride for Starliner’s astronauts, the two Crew-9 members will carry out their original goal of performing research at the ISS during their stay.

“While we’ve changed crew before for a variety of reasons, downsizing crew for this flight was another tough decision to adjust to given that the crew has trained as a crew of four,” NASA chief astronaut Joe Acaba said in a statement. “I have the utmost confidence in all our crew, who have been excellent throughout training for the mission.”

Meanwhile, Boeing’s Starliner spacecraft will autonomously undock from the ISS on September 6th at 6:04PM. It won’t have anyone onboard, but teams on the ground will be ready to “remotely command the spacecraft” if needed. The spacecraft is set to land in New Mexico’s White Sands Space Harbor around six hours later.