WASHINGTON - NASA blamed what it called engineering vulnerabilities in Boeing's Starliner spacecraft along with internal agency mistakes in a sharply critical report assessing a botched mission that left two astronauts stranded in space.
The US space agency labeled the 2024 test flight of the Starliner capsule a "Type A" mishap -- the same classification as the deadly Challenger and Columbia shuttle disasters -- a category that reflects the "potential for a significant mishap," it said.
The failures left a pair of NASA astronauts stranded aboard the International Space Station for nine months in a mission that captured global attention and became a political flashpoint.
"Starliner has design and engineering deficiencies that must be corrected, but the most troubling failure revealed by this investigation is not hardware. It's decision-making and leadership," said NASA administrator Jared Isaacman in a briefing.
"If left unchecked," he said, this mismanagement "could create a culture incompatible with human spaceflight."
The top space official said the investigation found that a concern for the reputation of Boeing's Starliner clouded an earlier internal probe into the incident.
"Programmatic advocacy exceeded reasonable bounds and place the mission, the crew and America's space program at risk in ways that were not fully understood at the time," Isaacman said.
He said Starliner currently "is less reliable for crew survival than other crewed vehicles" and that "NASA will not fly another crew on Starliner until technical causes are understood and corrected" and a problematic propulsion system is fixed.
But the administrator insisted that "NASA will continue to work with Boeing, as we do all of our partners that are undertaking test flights."
In a statement, Boeing said it has "made substantial progress on corrective actions for technical challenges we encountered and driven significant cultural changes across the team that directly align with the findings in the report."