NASA astronauts Butch Wilmore and Suni Williams arrived at the ISS aboard Boeing's Starliner spacecraft last June. The duo were flying the capsule's first crewed flight test, which was expected to stay in orbit for about 10 days before flying the pair back to Earth.

Nasa decided that it would not take even a small risk in bringing back Butch and Suni on Starliner, when they had the option of returning them on SpaceX's Dragon capsule. Nasa decided the best option was to do this during a scheduled crew rotation, even though it would mean keeping the astronauts on the space station for several months.