Boeing's troubled Starliner capsule that left two NASA astronauts on the International Space Station last year may need to fly a third uncrewed test flight before it carries astronauts again, agency officials said as the spacecraft's first crew had to return to Earth on a SpaceX capsule this week.

NASA and Boeing are still working on the problems that cropped up during Starliner's first crewed flight, which launched more than nine months ago.