This delay isn't a surprise. Last week, Boeing admitted to Ars Technica that a hot-fire test of Starliner's abort engines led to a propellant leak. The company has to fix the issue and complete a successful launch pad abort test before it can undertake a crewed test of the vehicle.

While SpaceX is scheduled to perform an uncrewed test sometime this month and a crewed test in December, it is unlikely to be able to meet those dates. The company is working with NASA to iron out some continuing issues, but it's uncertain how long it will take before Crew Dragon is ready for crewed testing.

Update (2:10 PM ET): NASA has officially delayed SpaceX's commercial crew test missions as well. Uncrewed is scheduled for November 2018, while the crewed test launch is scheduled for April 2019.