NASA has postponed its first launch of astronauts from US soil in almost a decade due to bad weather.
Just minutes before lift-off on Wednesday, the space agency announced the decision to stand down.
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.
For safety reasons NASA has postponed the mission, which had been planned in conjunction with Elon Musk's private spaceflight company SpaceX.
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 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 now launch is this weekend, with potential windows available on both Saturday and Sunday.
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.
A 10 minute delay was requested to reach this clearing period, but it was denied due to the immediate launch point rather than a window the mission could launch during.