Nasa and SpaceX are now aiming for a March debut of the first commercial crew capsule.
No one will be on board for the crew Dragon’s inaugural test flight to the International Space Station.
Officials on Wednesday set March 2 as the latest launch date.
If it goes well, two Nasa astronauts will take a test flight in July.
It would be the first launch of US astronauts into orbit, from US soil, since Nasa’s shuttle programme ended in 2011.
Boeing is shooting for an April launch of its first Starliner capsule without a crew.
The first Starliner flight with astronauts would be August at best.
Nasa’s commercial crew programme has been delayed repeatedly over the years, forcing a lengthy, expensive reliance on Russian rockets.