The historic SpaceX and NASA space mission has been aborted due to weather concerns.
Unfavourable atmospheric conditions prompted controllers to call off the mission just 16 minutes before the designated launch time.
For the first time, astronauts Bob Behnken and Doug Hurley were to head to the International Space Station from the Kennedy Space Center aboard a craft - the Falcon 9 rocket - made by a commercial company instead of a government agency.
Thursday (NZ time) would have marked the first orbital mission from the US in nine years.
NASA was providing the crew and SpaceX the hardware.
The launch will next be attempted on Sunday, May 31 at 7:22am (NZ time). If the second opportunity is also called off, a third has been scheduled for Monday (NZ time).
Until then, Behnken and Hurley will head back to quarantine.
Frustratingly, conditions just 10 minutes after what would have been lift-off (4:33pm local time - 8:33am NZ time) were acceptable, BBC News reports.
The "scrub sequence", where propellant is unloaded from the rocket, is now underway.
Following that, the astronauts will be able to disembark.
