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.

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.

A four-member crew including two astronauts from NASA, one each from Japan and Russia will replace Wilmore, Sunita Williams in the ISS. NASA to next attempt launch on Friday