Astronauts Butch Wilmore and Suni Williams will remain on the International Space Station until February 2025.

Boeing’s Starliner spacecraft has landed in New Mexico, completing a three-month test mission during which technical problems arose and the two astronauts on board had to be temporarily left behind in space.

The spacecraft landed at White Sands Space Harbor in the New Mexico desert at 04:01 GMT on Saturday. The two crew members it carried into space – Butch Wilmore and Suni Williams – remained on the International Space Station (ISS) for safety reasons.

Their return to Earth is expected next February.

According to a NASA livestream, the Starliner’s six-hour journey to Earth appeared to go smoothly. Despite earlier problems with its engines, the satellite mastered the critical final phase of its mission.

The spacecraft re-entered Earth’s atmosphere at around 11pm Friday (0300 GMT Saturday). About 45 minutes later, it opened a series of parachutes to slow its descent and inflated a series of airbags just before landing at the spaceport in New Mexico at 12:01am (0401 GMT).

“Demoralizing”

The mission was intended to be a final test flight before the US space agency NASA certifies the Starliner for routine missions, but the agency’s decision not to allow astronauts in the capsule for safety reasons has thrown the spacecraft’s certification path into disarray, despite Boeing making a clean return.

Wilmore and Williams, whose mission was initially planned to last only eight days, are scheduled to return to Earth in February 2025 on a space shuttle from Boeing competitor SpaceX, which is owned by Elon Musk.

“It must be demoralising in some ways when you expect to be up there for eight days and suddenly the mission extends to eight months,” Tanya Harrison, a fellow at the University of British Columbia’s Outer Space Institute, told Al Jazeera.

“At the same time, they are a highly trained team that knows that something like this can happen … they are trained, they are prepared,” she said.

During the Starliner’s ascent into space in June, with Wilmore and Williams aboard, five of the spacecraft’s 28 maneuvering thrusters failed. The same propulsion system also experienced multiple leaks of helium, which is used to pressurize the engines.

The malfunctions triggered an intensive investigation by Boeing – with the support of NASA – that cost the company $125 million.

Boeing, already reeling from safety concerns with its passenger aircraft, has said it can be trusted to bring the astronauts home. However, NASA does not share this assessment.

“Boeing believed in the model they developed to predict engine wear for the remainder of the flight,” said Steve Stich, program manager for NASA’s Commercial Crew Program.

But “due to the uncertainties in the modeling, the NASA team could not come to terms with it,” he added, describing the mood during the meetings as “tense.”

Repeated disturbances

The technical problems are not the first to plague the Starliner during test flights. One of them failed in 2019. Even though its repeat mission in 2022 was successful, there were some malfunctions in its engines then too.

The space giant’s problems with its Starliner have threatened its status in space, a field it dominated for decades until SpaceX began offering cheaper launches for satellites and astronauts and reshaped NASA’s collaboration with private companies.

Boeing will recover the Starliner capsule after landing and continue to investigate why the engines failed in space.