NASA and SpaceX on Wednesday delayed the launch of a replacement crew of four astronauts to the International Space Station that would have set in motion the long-awaited homecoming of U.S. astronauts Butch Wilmore and Suni Williams.

CAPE CANAVERAL, Fla. — A launch pad problem prompted SpaceX to delay a flight to the International Space Station on Wednesday 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.

Space X will launch a Crew-10 mission craft to return two astronauts who have been stranded at the International Space Station since September.