An historic US space flight that would have been visible from the UK was aborted shortly before launch due to bad weather.
NASA announced the decision on safety grounds just minutes before lift-off on Wednesday – with the flight now not happening until at least the weekend.
The mission had been planned in conjunction with Elon Musk’s spaceflight company SpaceX – and it would have been the first private involvement in taking astronauts to the International Space Station.
The US Air Force’s 45th Weather Squadron had forecast between a 40% and 60% chance of favourable conditions at the launch site in Florida.
Throughout the day weather conditions became worse, with a tropical storm initially threatening the launch before a tornado warning was issued.
NASA has stringent rules about the conditions in which the Falcon 9 can fly, and said one of these rules was being violated just minutes before the launch.
The earliest the SpaceX Falcon 9 rocket and the Crew Dragon spacecraft could now launch is this weekend, with potential windows available on both Saturday and Sunday.
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Falcon 9 rockets are not allowed to launch for 30 minutes after lightning is observed within 10 nautical miles of the launch pad and flight path.
NASA astronaut Anne McClain praised the SpaceX and NASA teams for “making the tough call” to postpone the mission.
“We all wanted a launch, but keeping our friends safe while we do it is a no-fail mission,” Ms McClain said, adding: “See you again Saturday.”
Although Donald Trump flew down to Florida to watch the launch, it being postponed means that the last president to be present at a NASA launch was Bill Clinton.
Barack Obama had flown to the Kennedy Space Centre for a space shuttle launch in 2010, but that launch was scrubbed due to a technical problem.
He didn’t return for the rescheduled launch a number of weeks later.
It isn’t clear whether Mr Trump will be back in Florida on Saturday.
Just a few miles away from the launchpad at the Kennedy Space Centre there is a Space Mirror Memorial.
It commemorates the 15 NASA astronauts who lost their lives while in service to the agency during a spaceflight.
No names will be added to that memorial due to decisions made today.