It has now been eight weeks since Boeing's Starliner spacecraft launched into orbit on an Atlas V rocket, bound for the International Space Station. At the time NASA officials said the two crew members, Butch Wilmore and Suni Williams, could return to Earth as soon as June 14, just eight days later.

Yes, there had been some problems on Starliner's ride to the space station that involved helium leaks and failing thrusters. But officials said they were relatively minor and sought to downplay them. "Those are pretty small, really, issues to deal with," Mark Nappi, vice president and manager of Boeing's Commercial Crew Program, said during a post-docking news conference. "We’ll figure them out for the next mission. I don’t see these as significant at all."

But days turned to weeks, and weeks turned to months as NASA and Boeing continued to study the two technical problems. Of these issues, the more pressing concern was the failure of multiple reaction control system thrusters that are essential to steering Starliner during its departure from the space station and setting up a critical engine burn to enter Earth's atmosphere.

In the last few weeks, ground teams from NASA and Boeing completed testing of a thruster on a test stand at White Sands, New Mexico. Then, last weekend, Boeing and NASA fired the spacecraft's thrusters in orbit to check their performance while docked at the space station. NASA has said preliminary results from these tests were helpful.

Dragon becomes a real option

One week ago, the last time NASA officials spoke to the media, the agency's program manager for commercial crew, Steve Stich, would not be drawn into discussing what would happen should NASA conclude that Starliner's thrusters were not reliable enough for the return journey to Earth.

“Our prime option is to complete the mission," Stich said one week ago. "There are a lot of good reasons to complete this mission and bring Butch and Suni home on Starliner. Starliner was designed, as a spacecraft, to have the crew in the cockpit."

For a long time, it seemed almost certain that the astronauts would return to Earth inside Starliner. However, there has been a lot of recent activity at NASA, Boeing, and SpaceX that suggests that Wilmore and Williams could come home aboard a Crew Dragon spacecraft rather than Starliner. Due to the critical importance of this mission, Ars is sharing what we know as of Thursday afternoon.

One informed source said it was greater than a 50-50 chance that the crew would come back on Dragon. Another source said it was significantly more likely than not they would. To be clear, NASA has not made a final decision. This probably will not happen until at least next week. It is likely that Jim Free, NASA's associate administrator, will make the call.

Asked if it was now more likely than not that Starliner's crew would return on Dragon, NASA spokesperson Josh Finch told Ars on Thursday evening, " NASA is evaluating all options for the return of agency astronauts Butch Wilmore and Suni Williams from the International Space Station as safely as possible. No decisions have been made and the agency will continue to provide updates on its planning."