NASA postponed the first crewed mission by Elon Musk’s SpaceX, citing bad weather at Kennedy Space Center in Cape Canaveral, Florida.

The launch window will move to May 30, the U.S. space agency said Wednesday. Astronauts Bob Behnken and Doug Hurley are set to ride SpaceX’s Dragon capsule to the International Space Station in the first launch of American astronauts from U.S. soil since 2011.

NASA will try again this weekend on the final major test of SpaceX’s human flight system before it can be certified to fly working missions to and from the orbiting lab. If the launch attempt May 30 gets scrubbed, the next day will serve as a backup.

Musk founded Space Exploration Technologies Corp. in 2002 with the ultimate goal of enabling people to live on other planets. NASA has been a key partner and customer every step of the way for the Hawthorne, California-based company. A cargo-only version of SpaceX’s Dragon capsule already makes regular runs to the space station.