Nasa astronauts from Boeing’s Starliner may be stuck in space until August

Engineers working on problems preventing return of Sunita Williams and Butch Wilmore, who are on the ISS

Two Nasa astronauts from Boeing's troubled Starliner capsule may have to remain in space until the middle of August as engineers continue to work through technical problems that prevented their return in June.

Sunita Williams and Butch Wilmore have been onboard the International Space Station (ISS) since 6 June after the first crewed docking of the next-generation spacecraft. The test mission was scheduled to last about a week, but Starliner's undocking was delayed several times as faulty thrusters and then a series of small helium leaks raised safety concerns.