Boeing's Starliner on its way back to Earth without NASA astronauts Sunita Willams, Barry Wilmore

Washington DC [US], September 7: Boeing's Starliner on Saturday got the final "go" that allowed the spacecraft, which left the International Space Station on Friday to return to Earth but the NASA astronauts Barry Wilmore and Sunita Williams it was supposed to be carrying are staying behind.

Boeing on Saturday morning said that the deorbit poll of the empty Starliner spacecraft has been completed and the landing phase will take 44 minutes from deorbit burn to landing.

Starliner switched to autonomous mode and undocked from the space station at 6:04 pm Eastern Time (2204 GMT), and is set to land at White Sands Space Harbor in New Mexico at approximately 12:00 am Eastern Time after after making its dangerous plunge back into the thick of Earth's atmosphere.

Both astronauts Sunita Williams and Butch Wilmore called down to flight controllers today to thank teams for their support before the uncrewed Starliner spacecraft returned to Earth.

"You guys it's time to bring Calypso home. We have your backs and you have got this. Bring her back to Earth," Sunita Williams said in the radio message referring to the spacecrafts nickname.

After it re-enters the Earth's atmosphere it will use parachutes to slow its descent to land at the White Sands Space Harbor in New Mexico.

While on its way back to Earth, the Starliner capsule, the portion that would hold astronauts during routine trips home from space, jettisoned its service module.

Thruster problems and helium leaks on the service module had caused issues that held up Starliner's return home and NASA and Boeing officials wanted to keep Starliner attached to the ISS for as long as possible so they could work to understand the leaks and thruster problems.

Barry "Butch" Wilmore and Sunita "Suni" Williams launched aboard Starliner on June 5 from Cape Canaveral in Florida for its first crewed flight, arriving at the orbiting International Space Station on June 6. It was expected that the two astronauts would have returned on the same flight.

As Starliner approached the orbiting laboratory, NASA and Boeing identified helium leaks and experienced issues with the spacecraft's reaction control thrusters.

For the safety of the astronauts, NASA announced on August 24 that Starliner will return to Earth from the station without a crew.

NASA said that while the Starliner makes its return to Earth, both Butch Wilmore and Sunita Williams are safe aboard the International Space Station with a SpaceX Dragon vehicle available in case of an emergency, and later as part of the Crew9 mission.

The uncrewed spacecraft's safe return could be vital for the overall Boeing Starliner program.

After the US space shuttle fleet was retired in 2011, the US relied solely on Russia's Soyuz spacecraft to transport its crew and cargo to the ISS.

The US space agency NASA then in the year 2014 awarded two American companies Boeing and Space X contracts to provide commercial spaceflights to take astronauts to space.

So far SpaceX has sent nine crewed flights to space for Nasa, as well as some commercial missions.

However for Boeign, the Starliner flight with Williams and Wilmore was its first crewed flight.