On Friday, a Boeing Starliner spacecraft undocked from the International Space Station to return to Earth without its crew. NASA astronauts Suni Williams and Butch Wilmore stayed behind due to uncertainty about the safety of the Boeing craft. The duo will instead hitch a ride back on a SpaceX mission set to arrive at the ISS in February. It’s another win for the Elon Musk-owned company, which has come to dominate rocket launches in the U.S. But NASA’s reliance on SpaceX now is a bit of a reversal, according to Steven Feldstein, senior fellow at the Carnegie Endowment’s Democracy, Conflict and Governance program.