Boeing's beleaguered Starliner returned to Earth without the astronauts who travelled in it to the International Space Station, after NASA deemed the risk too great.
The gumdrop-shaped capsule landed gently at the White Sands Space Harbor in New Mexico earlier this morning, its descent slowed by parachutes and cushioned by airbags, having departed the ISS around six hours earlier.
After years of delays, Starliner launched in June for what was meant to be a roughly week long test mission - a final shakedown before it could finally be certified to ferry crew to and from the orbital laboratory.
But unexpected thruster malfunctions and helium leaks on its way up derailed those plans, and NASA ultimately decided it was safer to bring astronauts Butch Wilmore and Suni Williams back on a rival SpaceX Crew Dragon - though they will have to wait until next February.
The century-old aerospace giant had carried out extensive ground testing aimed at replicating the technical issues the spaceship had experienced on its ascent, and devised plans to prevent more problems.
With its reputation already battered by safety concerns affecting its passenger jets, Boeing made assurances in public and in private that it could be trusted to bring the astronauts home - an assessment not shared by NASA.
"Boeing believed in the model that they had created that tried to predict the thruster degradation for the rest of the flight," Steve Stich, programme manager for NASA's Commercial Crew Programme, told reporters this week.
But "the NASA team, due to the uncertainty in the modelling, could not get comfortable with that," he added, characterising the mood during meetings as "tense."
Shortly after undocking, Starliner performed a powerful "breakout burn" to quickly send it clear of the station to prevent a collision - a manoeuver that would have been unnecessary if it had crew aboard who could take manual control of the ship if needed.
NASA awarded Boeing and SpaceX multibillion-dollar contracts a decade ago to develop spacecraft to ferry astronauts to and from the ISS, following the end of the Space Shuttle programme, which had left the US space agency reliant on Russian rockets for rides.
Elon Musk's SpaceX, initially considered the underdog, beat Boeing to the punch, and has successfully flown dozens of astronauts since 2020.
The Starliner programme, meanwhile, has been plagued by setbacks.
In 2019, during a first uncrewed test flight, a software defect meant the capsule failed to rendezvous with the ISS. A second software bug could have caused a catastrophic collision between its modules, but was caught and fixed just in time.
Then in 2021, with the rocket on the launchpad for a new flight, blocked valves forced another postponement.
The ship finally reached the ISS in May 2022 on a non-crewed launch. But other problems including weak parachutes and flammable tape in the cabin that needed to be removed caused further delays to the crewed test.
For the current mission, Captain Wilmore and Ms Williams were strapped into their seats and ready to fly twice before late "scrubs" due to technical hitches sent them back to their quarters.
