After an initial delay from late 2017 into early 2018, Boeing has acknowledged a second slippage of its schedule for the first commercial crew flights of its Starliner spacecraft. According to a report in Aviation Week, the company now says it will not be ready to begin operational flights until December 2018, a full year after NASA had originally hoped its commercial crew providers would be ready.

The admission by Boeing confirms a report by NASA's Inspector General, which found significant delays with both the Boeing and SpaceX efforts to develop private spacecraft to ferry US astronauts to and from the International Space Station. The delay also explains why, as Ars has previously reported, senior managers with the International Space Station program are likely to press ahead with the politically painful decision to purchase Soyuz seats for the calendar year 2019.

Boeing's second delay appears to have been caused by supply chain issues and other factors, which Boeing Program Manager for Commercial Crew John Mulholland said have been largely resolved. "When we were faced with these issues it was time for us to step back and say: ‘Hey listen, we have to readdress [this] and say what’s real and lay in where we are going forward,'” he told Aviation Week.

With the revised schedule, Boeing now anticipates completing an initial test crew flight in August 2018. Under this plan, the company could still receive certification from NASA in late 2018 and fly its first operational mission to the station by the end of the year.

NASA's other commercial crew provider, SpaceX, has had two issues with its Falcon 9 rocket, which will launch its crewed Dragon spacecraft into orbit. Despite this the company said flights in 2017 remain possible. “We continue to review and analyze data from the anomaly," a spokesman told Ars. "We expect to stay on track with our commercial crew milestones with NASA, but we'll better know how our schedule will be impacted once the investigation is complete and we get back to flying."

Nevertheless, the inspector general's report said SpaceX, too, had experienced issues with its spacecraft, particularly adjusting to water-based landings upon returning to Earth. Sources familiar with the commercial crew program have indicated to Ars that the race between SpaceX and Boeing to launch the first NASA astronauts from US soil remains too close to call.