Problems with Boeing's Starliner capsule forced Suni Williams and Butch Wilmore to stay on the International Space Station far longer than planned. At long last, the astronauts are en route back to Earth on a SpaceX Dragon capsule.

Their return caps a protracted space mission that was fraught with uncertainty and technical troubles and turned a rare instance of NASA's contingency planning - and the latest failures of Boeing's Starliner - into a global spectacle.

NASA astronauts Butch Wilmore and Suni Williams set out for a weeklong mission at the International Space Station last year. After nine months, they are coming home.