After months of unrest about its safety, Boeing’s new astronaut capsule left the International Space Station on Friday without a crew and made its way back to Earth.

NASA’s two test pilots remained in the space station – their home until next year – as the Starliner capsule undocked and was gently pushed away from the orbiting laboratory by springs.

The return flight was supposed to take six hours and land in the New Mexico desert at night.

“Bring them back to Earth. Good luck,” astronaut Suni Williams said to Boeing mission control before the Starliner’s departure.

Williams and Butch Wilmore were supposed to fly back to Earth on the Starliner in June, a week after launch. But engine failures and helium leaks marred their flight to the space station.

NASA ultimately decided that it was too risky to bring the duo back on the Starliner.

So the fully automated capsule left the facility with empty seats and blue space suits as well as some old station equipment.

SpaceX will bring the duo back in late February, extending their original eight-day mission to more than eight months.

Boeing’s first astronaut flight crowns a journey full of delays and setbacks.

After the space shuttles were retired over a decade ago, NASA contracted Boeing and SpaceX to provide orbital taxi services.

Boeing’s first uncrewed test flight in 2019 encountered so many problems that the flight had to be repeated.

When it was repeated in 2022, even more defects were uncovered and repair costs exceeded the $1 billion mark.

SpaceX’s crew transport flight later this month will be NASA’s tenth since 2020.

The Dragon capsule will launch on the six-month expedition with only two astronauts, as two seats are reserved for Wilmore and Williams on the return flight.

As experienced astronauts and retired Navy captains, Wilmore and Williams expected there would be obstacles during the test flight.

They were employed in space, helping with repairs and experiments.

The two are now full-time members of the station crew, along with the seven others on board.

Even before the pair’s launch on June 5, helium leaked from the Starliner’s propulsion system.

The leak was small and considered isolated, but four more occurred after takeoff.

Then five engines failed.

Although four engines were recovered, NASA feared that further malfunctions could hinder the capsule’s descent from orbit.

Boeing conducted numerous engine tests in space and on the ground over the summer and was confident that its spacecraft could bring Wilmore and Williams home safely.

But NASA disagreed and chose SpaceX.

Flight control planned further test firings of the engines after the capsule was undocked.

Engineers suspect that as the ignition progresses, the engines get hotter, causing the protective seals to swell and impede fuel flow.

They will not be able to examine any parts because the section containing the engines will be jettisoned shortly before re-entry.

Steve Stich, NASA’s commercial crew program manager, said earlier this week that teams were so focused on the Starliner’s return that they hadn’t had time to think about what’s next for Boeing.

He said the space agency remains committed to having astronaut transportation handled by two competing U.S. companies.