It now seems likely that Starliner will not launch crew until early 2022 - Ars Technica

This test flight of Starliner, which will not carry crew, is destined to launch on an Atlas V rocket and dock with the International Space Station for about a week before returning to Earth.

The primary issue is the availability of space station docking ports fitted with an "international docking adapter," which are used by SpaceX's Crew Dragon, Cargo Dragon 2, and Starliner vehicles.

The Crew-2 mission, carrying four astronauts on SpaceX's Crew Dragon vehicle, is expected to launch on April 22 and remain attached to one of these ports for about six months.

The upcoming Starliner test flight will be the vehicle's second uncrewed flight, which was necessitated after a problematic test mission in December 2019.

After this repeat test flight, which is officially known as Orbital Flight Test-2, NASA and Boeing will perform a detailed data analysis.

Another NASA official said the spacecraft would not fly until the "hardware is ready and it makes the most sense to fly based on station's needs." He added that there is no clock on this crewed flight test, since NASA already has an operational vehicle, Crew Dragon, to meet its astronaut-rotation needs.

One source expressed "hope" that a 2021 launch date could be found for Starliner's crew test flight, but more realistically, the mission will slip into 2022.

A source with knowledge of space station flight schedules suggested that the best opportunity for Starliner's crewed flight test, commanded by astronaut Butch Wilmore, would likely come in February 2022.

Finally, if this crew test flight is successful, Boeing could fly its first "operational" Starliner mission for NASA.