WASHINGTON — NASA and Boeing say they are working towards the first crewed flight of the CST-100 Starliner spacecraft in early May, a final milestone before the vehicle is cleared for regular flights to the International Space Station.

At a series of briefings March 22, NASA and Boeing officials said preparations for the Crew Flight Test (CFT) mission are proceeding well, with a launch scheduled for no earlier than May 1. That schedule is driven by the ISS manifest of visiting vehicles, which earlier this month delayed the mission from late April.

That mission will send NASA astronauts Butch Wilmore and Suni Williams to the station, where they will spend about eight days before returning to land in the southwestern United States. The flight will take place nearly two years after a second uncrewed flight test, OFT-2, that also docked with the station.

“The CFT flight is really the introduction of crew into our vehicle systems, so a lot of our flight test objectives are about how that interface will work,” said Mark Nappi, vice president and Starliner program manager at Boeing. “It’s all about, does the vehicle perform with the human in the loop as expected?”

Those test objectives range from the performance of the spacecraft’s life support systems to the use of manual controls to operate the spacecraft should automated systems fail. Wilmore and Williams will test the ability to manually control and orient the spacecraft during a day-long flight to the ISS, and test maneuvering during a 6.5-hour trip from the station back to the ground.

“It’s a test pilot’s dream, if you will, everything that we’re doing from start to finish,” said Wilmore at another briefing.

CFT will be the final major milestone before NASA formally certifies the spacecraft for crew rotation flights, starting with the Starliner-1 mission in early 2025. “OFT-2 was the path to the Crew Flight Test, and this Crew Flight Test is the path to Starliner-1,” said Steve Stich, NASA commercial crew program manager.

That certification is expected to be complete in November or December, unless any issues come up during CFT. “It kind of needs to happen in that timeframe to hit the spring slot” for Starliner-1, he said. “I think we have a good shot. We just need to stay on track.”

Stich said NASA was still wrapping up a few certification items for CFT, including completing the review of data from a parachute test earlier this year that validated a redesigned “soft link” that was a factor in delaying the mission from last year, as well as completing analyses of abort modes. Neither appeared to pose a risk of further delays. “We’re in really good shape,” he said.

Getting Starliner into operational missions, albeit years behind schedule, is still desired by NASA to ensure redundancy in access to the ISS, backstopping SpaceX’s Crew Dragon. “We are really excited on the station side to get this first crewed Boeing Starliner mission up to the space station,” said Dana Weigel, NASA ISS deputy program manager. “It’s always been our goal to have a handful of different vehicles that we can fly to get crew up there.”

Nappi said that Boeing’s focus is getting Starliner into operation for NASA, fulfilling a contract awarded nearly a decade ago for six ISS flights, and is not actively considering other private mission for the spacecraft for now. “The private astronaut missions are of interest later in the decade,” he said, but only after operational missions begin.

One of the people who has waited the longest for CFT is Williams, who was named by NASA in 2015 to a “cadre” of astronauts who would train for the first commercial crew missions. “It’s been a little bit of a timeline” to get to this point just before launch, she said at the briefing, but agreed with Wilmore that flying this mission is a “test pilot’s dream” for her. “I don’t think I would really want to be in any other place right now.”

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...