Nasa astronauts Doug Hurley and Bob Behnken have completed their dress rehearsal for Wednesday's flight to the International Space Station.
The mission, the first crewed outing from American soil in nine years, will see the pair ride to orbit in a SpaceX Falcon rocket and Crew Dragon capsule.
It's a demonstration of the new "taxi" service the US space agency will be buying from the Californian firm.
Lift-off on Wednesday is timed for 16:33 EDT (20:33 GMT / 21:33 BST).
The weather around the Kennedy Space Center in Florida may have other ideas, however.
A forecast released on Saturday by the US Air Force 45th Weather Squadron predicted just a 40% chance of favourable conditions come launch time.
There is a strong possibility the Kennedy complex could see thick cloud, rain and even thunder.
If controllers are forced to scrub, everyone will come back on Saturday for a second try.
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