SpaceX scrubbed plans to launch the first American astronauts into orbit from U.S. soil on Wednesday as thunderstorms tore through Florida’s Space Coast, temporarily thwarting a highly anticipated test that could determine the future of American space flight.

Astronauts Doug Hurley and Robert Behnken were slated to blast off to the International Space Station (ISS) aboard SpaceX’s Dragon Crew capsule at 4:33 p.m.