NASA engineers are running checks to solve the mystery of why the Falcon 9's engine failed to perform a routine maneuver to lower the rocket's altitude.

The Dragon Crew 9 capsule has docked with the International Space Station, carrying a U.S. astronaut and a Russian cosmonaut. The craft will bring home two astronauts stranded on the International Space Station.

The SpaceX Crew-9 Dragon will dock at the International Space Station Sunday afternoon. After a successful launch on Saturday, the two-man crew will be docking at the ISS. The Dargon spacecraft, which is supporting this mission, previously flew the Crew-4, Ax-2, and Ax-3 missions to and from the International Space Station.