— SpaceX's Starlink broadband satellites could be used for GPS navigation Another of those 15 was a crewed flight — the April 8 launch of the Ax-1 mission, which sent four private astronauts to the International Space Station. And SpaceX has another crewed flight coming up soon as well — the Crew-4 mission for NASA, which will send four professional spaceflyers to the orbiting lab for a lengthy stay. Crew-4 is currently scheduled to lift off no earlier than April 26. That date recently slipped a few days due to bad weather in the projected splashdown zone for Ax-1, which pushed that mission's planned departure from the station from Tuesday (April 19) to Saturday (April 23). NASA officials have said they want at least a two-day window between Ax-1's splashdown and Crew-4's launch. Editor's note: This story was updated at 2:10 p.m. EDT (1810 GMT) with news of successful liftoff, then again at 6 p.m. EDT (2200 GMT) with news of satellite deployment. Mike Wall is the author of "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or on Facebook. Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: community@space.com.