SpaceX and NASA are gearing up for a historic mission: On Saturday, they plan to launch humans in a commercial spacecraft for the first time ever and restore the US’s ability to send its own astronauts into space.

If clouds don’t delay the launch again (as they did on Wednesday), NASA astronauts Bob Behnken and Doug Hurley will board SpaceX’s Crew Dragon spaceship, perched atop its Falcon 9 rocket, and hurtle into Earth’s orbit. The plan calls for them to reach the International Space Station on Sunday morning.