WASHINGTON. Boeing’s Starliner spacecraft successfully returned to Earth late Friday, landing in the New Mexico desert without astronauts aboard, concluding a three-month test mission plagued by technical issues. Originally intended to be a crewed mission, safety concerns forced NASA to leave its astronauts on the International Space Station (ISS) until next year.

Starliner autonomously undocked from the ISS at 6:04 p.m. ET (2204 GMT), beginning a six-hour journey back to Earth. NASA had previously deemed the spacecraft’s maneuvering thrusters too risky for the crew, leading to the decision to send the capsule back uncrewed. NASA astronauts Butch Wilmore and Suni Williams, who were originally scheduled to return on Starliner, remained on the ISS.

The spacecraft reentered Earth’s atmosphere at about 11 p.m. ET, traveling at orbital speeds of 17,000 miles per hour (27,400 kilometers per hour). Forty-five minutes later, it deployed parachutes and inflated airbags to ensure a safe landing at White Sands Space Harbor in New Mexico.

While the mission’s successful return marked an important step, the decision to fly the spacecraft uncrewed due to safety concerns complicates Boeing’s efforts to have Starliner certified for regular missions. NASA’s choice to keep Wilmore and Williams off the capsule reflects ongoing uncertainty about Starliner’s future.

Wilmore and Williams, who have been aboard the ISS since June, were initially supposed to return to Earth after just eight days. However, due to technical issues with Starliner, their mission has been extended to February 2025, when they are expected to return on a SpaceX vehicle.

The ISS, a massive science laboratory orbiting 250 miles (402 kilometers) above Earth, currently hosts seven other astronauts who arrived on various spacecraft, including a Russian Soyuz capsule. Wilmore and Williams will continue conducting scientific experiments alongside their fellow crewmates.

The trouble began in June when five of Starliner’s 28 maneuvering thrusters malfunctioned during the spacecraft’s approach to the ISS. Additionally, the propulsion system experienced multiple helium leaks, used to pressurize the thrusters. Despite these failures, Starliner successfully docked at the ISS on June 6.

Boeing and NASA launched an extensive investigation into the thruster malfunctions, costing Boeing $125 million. Since the program began in 2016, Boeing has now accumulated over $1.6 billion in cost overruns, according to a Reuters analysis of securities filings. This test flight was supposed to be Starliner’s final step before routine missions, but safety concerns have pushed its certification into question.

Boeing’s Starliner program has faced setbacks since a failed uncrewed test flight in 2019. Though a 2022 re-do mission was largely successful, it also experienced thruster malfunctions.

As Boeing investigates the cause of the thruster issues, the service module, which housed the failed thrusters, detached from Starliner as designed and burned up upon reentry. Boeing will rely on simulated tests to diagnose what went wrong with the hardware during the mission.

With SpaceX offering more cost-effective launches for both satellites and astronauts, Boeing faces increased pressure to secure its future in space—a domain it had once dominated.