NASA and Boeing identified helium leaks and experienced issues with the spacecraft reaction control thrusters on June 6 as Starliner approached the space station. Since then, engineering teams have completed a significant amount of work, including reviewing a collection of data, conducting flight and ground testing, hosting independent reviews with agency propulsion experts, and developing various return contingency plans. The uncertainty and lack of expert concurrence does not meet the agency’s safety and performance requirements for human spaceflight, thus prompting NASA leadership to move the astronauts to the Crew-9 mission.

“Decisions like this are never easy, but I want to commend our NASA and Boeing teams for their thorough analysis, transparent discussions, and focus on safety during the Crew Flight Test,” said Ken Bowersox, associate administrator for NASA’s Space Operations Mission Directorate. “We’ve learned a lot about the spacecraft during its journey to the station and its docked operations. We also will continue to gather more data about Starliner during the uncrewed return and improve the system for future flights to the space station.”