The astronauts will be brought home with a spacecraft from competitor Space X. Bringing them home with Boeing's new, problem-ridden Starliner capsule is considered too risky.
Nasa has decided that Butch and Suni will return with Crew-9 in February, and that Starliner will return unmanned, says Nasa chief Bill Nelson.
It hasn't been an easy decision, but it's the right one, he adds, referring to safety.
The announcement is considered a major setback for Boeing.
Starliner was affected during the journey, among other things, by helium leakage and problems with fuel supply. Moreover, five steering rockets stopped functioning.
The launch of the spacecraft Starliner has been postponed several times, but was finally carried out on June 5. The astronauts, Butch Wilmore and Suni Williams, were originally planned to stay on the ISS for just over a week.
