Two Nasa astronauts on Boeing’s Starliner capsule will remain at the International Space Station with no official return date yet, Nasa and Boeing officials said on Thursday morning, as engineers continue to examine the technical problems with the spacecraft. Test pilots Butch Wilmore and Sunita Williams first departed for the station roughly seven weeks ago, in early June, on a test mission that was meant to last about a week. But the capsule’s undocking was delayed because of faulty thrusters and small helium leaks that raised safety concerns. Last month, a spokesperson from Boeing said the helium leaks and most of the thruster problems had been “all stable and not a concern for the return mission”. “Four of the five thrusters that were previously shutting down are now operating normally. This means only one thruster out of 27 is currently offline. This does not present an issue for the return mission,” the spokesperson said at the time. Nasa and Boeing officials have said that the astronauts are not stranded and that the technical difficulties do not threaten the mission. Earlier this month, Nasa announced it was still performing tests to ensure the capsule would perform as expected, and said that even though they were confident the craft would be safe for an emergency evacuation, the mission managers were not yet ready to schedule its departure. On Thursday, Nasa and Boeing officials said they were not ready to announce a return date, and that the pilots would remain at the space station until the engineers finish working on and examining the issues with the capsule. “We’ll come home when we’re ready,” Steve Stich, Nasa’s commercial crew program manager said in the press conference, according to the Associated Press. He also acknowledged that backup options are under review, including using other capsules to get the astronauts home safely, which he said was a top priority. Engineers recently completed testing on a spare thruster in the New Mexico desert, according to Nasa, which will be further examined in an attempt to understand what went wrong. According to AP, officials say that the issues appear to have been caused by degraded seals, though more analysis is needed. This is not the first time the Starliner mission, which is the first time the spacecraft has carried a crew to space, has dealt with technical issues. This Nasa-Boeing mission had difficulties before its launch too, including problems with reaction control thrusters and helium leaks, which delayed its departure.