After months of turmoil over its safety, Boeing's new astronaut capsule is set to depart the International Space Station on Friday without its crew.

NASA's two test pilots will stay behind at the space station -- their home until next year -- as the Starliner capsule prepares to undock and aims for a touchdown six hours later in the New Mexico desert.

Butch Wilmore and Suni Williams should have flown Starliner back to Earth in June, a week after launching in it. But thruster failures and helium leaks marred their ride to the space station.

NASA ultimately decided it was too risky to return Wilmore and Williams on Starliner. So the capsule contains their empty seats and blue spacesuits along with some old station equipment. SpaceX will bring the duo back in late February, stretching their original eight-day mission to more than eight months.

Boeing's first astronaut flight caps a journey filled with delays and setbacks. After the space shuttles retired more than a decade ago, NASA hired Boeing and SpaceX for orbital taxi service. Boeing ran into so many problems on its first test flight with no one aboard in 2019 that it had to repeat it. The 2022 do-over uncovered even more flaws and the repair bill topped $1 billion.

SpaceX's crew ferry flight later this month will be its 10th for NASA since 2020. The Dragon capsule will launch on the half-year expedition with only two astronauts since two seats are reserved for Wilmore and Williams for the return leg.

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