According to NASA, the thrusters are used to maneuver the craft and guide it onto the right flight path. Further testing is required to determine why the issue was not detected during the most recent test.
In the meantime, the launch of one of SpaceX’s Dragon capsules has been delayed to give NASA and Boeing more time to solve the Starliner problem.
The SpaceX mission (known as Crew-9) was scheduled for later in August and would send four new crew members to the ISS.
NASA officials have said they could send two crew members to space on that vehicle instead of four so that Wilmore and Williams can return to Earth with them in February 2025.
NASA has not yet decided how and when to bring the astronauts home, but a final decision needs to be made by the middle of August.