NASA and SpaceX have postponed the launch of Crew-10, which was set to transport four astronauts to the International Space Station (ISS) and facilitate the long-awaited return of U.S. astronauts Butch Wilmore and Suni Williams. The launch, originally scheduled for Wednesday, was called off due to a hydraulic system issue with a ground support clamp arm for the Falcon 9 rocket, NASA confirmed in a statement.

The space agency now aims for a launch no earlier than Friday at 7:03 p.m. EDT (2303 GMT), after delaying a Thursday attempt due to unfavorable weather conditions. If the launch proceeds as planned, Wilmore and Williams—who have been stranded in space for nine months following issues with Boeing’s Starliner spacecraft—are expected to return to Earth on March 19.

The Crew-10 mission, initially planned for later in March, was expedited after calls from former U.S. President Donald Trump and SpaceX CEO Elon Musk to bring the astronauts back sooner than NASA had originally planned. The two veteran astronauts and former U.S. Navy test pilots had departed for the ISS in June 2023 aboard Boeing's Starliner, but the spacecraft suffered propulsion system issues, making its return trip unsafe.

While aboard the ISS, Wilmore and Williams have been assisting with research and maintenance activities alongside other astronauts. Williams recently expressed excitement about reuniting with her family and pets upon her return.

Crew-10’s upcoming launch from NASA’s Kennedy Space Center will carry two U.S. astronauts along with one astronaut from Japan and one from Russia. Once they arrive at the ISS, Wilmore, Williams, and two other crew members—NASA’s Nick Hague and Russian cosmonaut Aleksandr Gorbunov—will return to Earth in a SpaceX capsule that has been docked at the station since September.

The delay marks another setback for Boeing’s Starliner program, which was developed under a $4.5 billion NASA contract to compete with SpaceX’s Crew Dragon. Starliner’s prolonged technical challenges and cost overruns have left SpaceX as NASA’s primary provider for human spaceflight missions since 2020.