SpaceX will launch a crewed NASA mission on Friday to return two astronauts from the International Space Station, after technical issues with Boeing’s spacecraft extended their stay for nine months, leading SpaceX CEO Elon Musk and President Donald Trump to suggest they were stranded for “political reasons.

The launch will mean NASA astronauts Suni Williams and Butch Wilmore are finally closing in on their long-awaited flight back to Earth.

The Starliner, which was supposed to establish itself as a viable alternative, has faced issues that have raised questions about its reliability.

NASA and SpaceX on Wednesday night scrubbed the Falcon 9 launch of a flight intended to retrieve from the International Space Station astronauts Suni Williams and Butch Wilmore, who have spent nine months in orbit.

“Future built environments, including space stations, could benefit from intentionally fostering diverse microbial communities that better mimic the natural microbial exposures experienced on Earth, rather than relying on highly sanitized spaces,” says co-first author Rodolfo Salido at UC San Diego.

Watch SpaceX Crew-10 lift off on a mission to the International Space Station from Launch Complex 39A at NASA's Kennedy Space Center in Florida. This is the first leg of the mission to return NASA astronauts Sunita Williams and Barry Wilmore to Earth after their extended stay on the ISS following Boeing's failed Starliner Spacecraft,