NASA aims to use Boeing’s Starliner capsule for a crewed mission to the International Space Station as soon as February, the agency said. The flight will mark a major milestone in Starliner’s development, which has suffered from delays and testing setbacks.

The planned eight-day mission would be Starliner’s first with astronauts aboard. While the exact launch date hasn’t been set, February “is likely the best window,” Steve Stich, manager of NASA’s Commercial Crew Program, said Thursday in a news conference. The agency had previously said it hoped to launch by the end of this year.

NASA selected Boeing and Elon Musk’s SpaceX in 2014 to build and operate vehicles that will ferry crews to the space station. In June, NASA announced it had selected two astronauts to fly on Starliner’s first crewed flight.

The plans come on the heels of a successful uncrewed test flight in May that was a welcome development after years of setbacks. Boeing has accrued $595 million in charges to cover Starliner delays, including $185 million last October.

Despite recent stock performance gains, Boeing CEO Dave Calhoun has remained under fire from customers and investors as the company has grappled with problems in its commercial aircraft operations.