WASHINGTON — NASA announced Jan. 22 that it is replacing an astronaut who was scheduled to fly on a commercial crew test flight later this year because of a medical issue.

The agency said that Eric Boe has been taken off the crew of the Boeing CST-100 Starliner crewed test flight, and will be replaced by veteran NASA astronaut Mike Fincke. Boe will take over Fincke’s previous position as assistant to the chief of the astronaut office for commercial crew.

In its statement, NASA said only that Boe would no longer be able to fly on the Starliner test flight “due to medical reasons.” The other two people assigned to the flight, NASA astronaut Nicole Mann and former NASA astronaut Chris Ferguson, now a test pilot for Boeing, will remain on the flight.

Boe, 54, joined the NASA astronaut corps in 2000 and flew on two shuttle flights, STS-126 in 2008 and STS-133 in 2011. The latter flight was the last mission of the shuttle Discovery before its retirement, as the shuttle program wound down.

Fincke, 51, joined the NASA astronaut corps in 1996. He flew on two long-duration missions to the International Space Station on Soyuz spacecraft in 2004 and 2008–2009, as well as the final flight of the shuttle Endeavour, STS-134, in 2011. Fincke spent 381 days in space on those three missions, including more than 48 hours of EVA time on nine spacewalks.

NASA announced the original crew assignments for the CST-100 Starliner test flight and for a separate SpaceX Crew Dragon test flight in August. The agency also announced at the time crews for the first operational missions for those vehicles.

The latest schedule for commercial crew test flights calls for Boeing to perform an uncrewed test flight of Starliner in March, followed by the crewed test flight in August. NASA, in its statement announcing the change in crews, said only that the crewed test flight is scheduled for “later this year.”

The uncrewed test flight of SpaceX’s Crew Dragon spacecraft is now scheduled for February, NASA announced Jan. 10. That launch, previously scheduled for Jan. 17, was delayed to provide additional time “to complete hardware testing and joint reviews,” the agency said then. The Falcon 9 that will launch the spacecraft arrived at the Launch Complex 39A Jan. 22 for a static fire test expected as soon as Jan. 23. The crewed test flight will follow no earlier than June.