Nasa astronauts Suni Williams and Butch Wilmore have been left at the International Space Station (ISS) for nine months, after the Boeing Starliner capsule that carried them there encountered faults.

On 14 March, SpaceX launched a rocket carrying a new crew to the ISS, as part of a plan to bring the astronauts back to Earth.

Suni and Butch are due to begin their journey back to Earth two days after the new crew arrives, but conditions on Earth could delay the return.

The BBC’s Aruna Iyengar explains how the astronauts ended up on the ISS for nine months.

Video filmed and edited by Gabriela Boccaccio.

Video produced by Ian Casey and Rachel Flynn.