Nonetheless, the problems for Starliner raise the stakes for SpaceX’s next launch of its Crew Dragon capsule, currently scheduled for Jan. 11. That flight — without crew aboard — a test of the abort system, in which the rocket will be intentionally destroyed during launch. If that succeeds, SpaceX could still launch astronauts in the first half of 2020.

Boeing was also aiming for its first crewed flight in the first half of next year using a second Starliner. The Starliner currently in orbit is to be reused for the second crewed flight later in 2020.

Additional delays to Boeing’s schedule increase the possibility that NASA will have to reduce the number of astronauts living in its section of the space station. Even before Friday, the space agency was already talking to Russia about purchasing one or two additional seats on Soyuz rockets, the only means for getting to the space station for more than eight years since the retirement of NASA’s space shuttles in 2011.

In a shift from the space shuttles and NASA’s earlier human spaceflight programs, the Obama administration decided that the agency should hire commercial companies to take astronauts to and from the space station instead of building and operating its own spacecraft. The space agency had already taken this approach for launches of satellites and robotic missions, as well as for taking cargo to the space station.

In 2014, NASA awarded contracts to Boeing and SpaceX — Boeing for up to $4.3 billion for Starliner, SpaceX for up to $2.5 billion for Crew Dragon. The value of the contracts depends on how many missions are flown.

The hope was that the flights carrying astronauts would begin by the end of 2017. Both companies encountered technical hurdles, including problems with parachutes that the capsules deploy when they return to Earth.

SpaceX performed its crewless flight test of Crew Dragon in March. But in July, during a ground test of the abort engines on the same capsule, the Crew Dragon exploded. No one was injured, but that pushed back SpaceX’s schedule as the company figured out what happened and how to fix it.