Bad weather has prevented the first launch of Nasa astronauts from US soil in nine years, with the SpaceX capsule now due to attempt lift-off on Saturday.
Robert Behnken and Douglas Hurley were set to travel to the International Space Station (ISS) on a rocket and capsule system built by billionaire entrepreneur Elon Musk's firm SpaceX.
An estimated 1.7 million people from around the world tuned in to the launch from The Kennedy Space Center in Florida.
But as the weather conditions became worse, the US space agency postponed the mission for safety reasons.
The US Air Force's 45th Weather Squadron, which monitors the weather for air and space operations, had forecast between a 40pc and 60pc chance of favourable conditions at the launch site in Florida.
Nasa, which has strict rules about the conditions for manned crew missions, said of one these rules was being violated just minutes before the launch.
The earliest the SpaceX Falcon 9 rocket and the Crew Dragon spacecraft could depart is this weekend, with potential launch windows available on Saturday and Sunday.