WASHINGTON — Boeing announced Dec. 3 that it’s delaying the uncrewed test flight of the company’s CST-100 Starliner commercial crew vehicle by two days because of a minor launch vehicle issue.

In an on-stage interview during a U.S. Chamber of Commerce commercial space conference here, Jim Chilton, senior vice president of the space and launch division of Boeing Defense, Space and Security, said Boeing had just received range approval to slip the Orbital Flight Test (OFT) launch two days to Dec. 19 at 6:59 a.m. Eastern.

“We had something come up over the weekend on purge ducting,” Chilton said, adding it was “a little off” and that the company decided to take the time to correct the problem and delay the launch.

United Launch Alliance, which provides the Atlas 5 rocket that will launch the Starliner, said in a later statement it involved an air supply duct. “Additional time was needed for the ULA and Boeing teams to complete an analysis of the issue, replace the duct and complete processing ahead of launch,” ULA stated. An industry source said the duct in particular was for the cavity in the launch vehicle adapter between the bottom of the Starliner and the top of the rocket’s Centaur upper stage.

The Orbital Flight Test is an uncrewed test flight of the vehicle, similar to the Demo-1 mission conducted by SpaceX’s Crew Dragon spacecraft in March. The flight will test the vehicle’s capabilities, including docking with the International Space Station, over the course of about a week. The spacecraft will then land, with White Sands Missile Range in New Mexico the primary landing site.

That mission will be followed by a crewed test flight, with NASA astronauts Michael Fincke and Nicole Mann as well as Boeing astronaut Chris Ferguson on board. NASA has not set a date for that launch, but it is not expected before spring 2020.