Elon Musk’s rocket company signed up its first passenger for a flight around the moon, taking a giant leap toward commercializing space travel.

The person’s identity will be revealed on Sept. 17, Space Exploration Technologies Corp. said in a tweet. Asked whether he’d be the first passenger, Musk -- who’s also the chief executive officer of Tesla Inc. -- posted an emoji of a Japanese flag.

Musk’s SpaceX and Richard Branson’s Virgin Galactic LLC are among companies that are attempting to commercialize space travel. In July, billionaire Branson said he hoped to be sitting on a spaceship going to space before the end of the year.

SpaceX this month successfully launched a commercial satellite from Florida, marking the company’s 16th mission of 2018. Its valuation has climbed to about $28 billion, making it the third-most valuable venture-backed startup in the U.S. after Uber Technologies Inc. and Airbnb Inc.