NASA astronauts Sunita Williams and Butch Wilmore are scheduled to return to Earth tomorrow, Wednesday, after being stranded on International Space Station (ISS) for nine months due to spacecraft malfunction.

Originally intended as a brief mission, technical issues with their Boeing Starliner spacecraft prolonged their stay significantly.

Williams and Wilmore initially launched on June 5 last year aboard the Boeing Starliner for what supposed to be an eight-day mission. However, unexpected technical problems with the spacecraft extended their time in space dramatically.

NASA had been actively planning their safe return since last year. Following the inauguration of U.S. President Donald Trump in January, efforts to bring the astronauts back gained momentum.

As part of this mission NASA and SpaceX launched a Crew Dragon spacecraft from NASA’s Kennedy Space Center in Florida last Friday at 11:03 PM GMT.

After a 29-hour journey spacecraft successfully docked with ISS at 4:04 AM GMT on Sunday. Williams and Wilmore will return as part of a crew rotation, traveling with NASA astronaut Nick Hague and Russian cosmonaut Alexander Grebennikov.

Read more: Nine-Month Space Struggle Ends: Sunita Williams and Butch Wilmore Set to Return Home

Although the return schedule set NASA has indicated potential delays if unforeseen circumstances arise. Nonetheless, NASA continues to monitor conditions closely to ensure a successful mission.