STORY: Problems with Boeing's Starliner capsule have upended the original plans for the return of two astronauts to Earth, leaving them aboard the International Space Station as teams look at last-minute fixes.

:: June 5, 2024

Since its liftoff on June 5 the capsule has had five helium leaks, five maneuvering thrusters go dead and a propellant valve fail to close completely.

The current problems center on Starliner's expendable propulsion system, which is needed to back away from the ISS and position it to dive through Earth's atmosphere.

Starliner can stay docked at the ISS for up to 45 days, according to comments by NASA's commercial crew manager Steve Stich.

He said recent test-firings of the thrusters gave mission teams confidence in a safe return, though tests and reviews are ongoing.

A source who spoke on the condition of anonymity said internally, NASA's latest targeted return date is July 6.

That would mean the mission, originally planned for eight days, would instead last a month.

Even with the propulsion issues NASA has said Starliner would still be capable of returning the astronauts to Earth if absolutely necessary - that is, if the capsule must serve as an escape pod.

If Starliner is deemed incapable of safely returning Barry "Butch" Wilmore and Sunita "Suni" Williams, one option would be sending them home aboard SpaceX's Crew Dragon.

NASA and Boeing officials, as well as engineers familiar with the program, told Reuters nothing about Starliner's current problems indicates that this would be needed.

This is Starliner's first mission to orbit carrying astronauts - the final test needed before NASA can certify it as the U.S. space agency's second ride to the ISS.