When the new crew arrives aboard the station, Wilmore, Williams and two others - NASA astronaut Nick Hague and Russian cosmonaut Aleksandr Gorbunov - can return to Earth in a capsule that has been attached to the station since September, as part of the prior Crew-9 mission.
If Crew-10 launches as planned on Friday, it will dock to the ISS at 11:30 pm Saturday, followed by a traditional handover ceremony that will allow for the Crew-9 crew's departure March 19.
Wilmore and Williams cannot leave until the new Crew-10 craft arrives so that the ISS staffed with enough U.S. astronauts for maintenance, according to NASA.