SpaceX's Falcon 9 rocket lifted off at 7:03 p.m. ET (2303 GMT) from NASA's Kennedy Space Center in Florida carrying four astronauts who will replace Wilmore and Williams, both of whom are veteran NASA astronauts and retired U.

A SpaceX capsule carrying a fresh crew to the space station launched Friday, setting the stage for the Starliner astronauts to finally come home.

A launch pad problem has forced a flight delay to replace NASA's two stuck astronauts. The new crew needs to get to the International Space Station before Butch Wilmore and Suni Williams can head home after nine months in orbit.