NASA astronauts stranded due to Boeing's faulty Starliner received horrifying news on Wednesday about their return mission to Earth.

Suni Williams and Butch Wilmore, who have already been trapped on the International Space Station (ISS) for more than two months, may not come back to Earth until February 2025.

The US space agency revealed a contingency plan that would launch a two-person crew on SpaceX's Crew-9 mission in September, but still wouldn't bring the crew home until months later.

The announcement is another highly embarrassing blow for the embattled Boeing, which is dealing with a spate of issues plaguing its commercial jets.

Tuesday marked 60 days the Starliner crew has been in space - instead the intended eight day mission.

Thruster failures and helium leaks on Starliner prompted NASA and Boeing to keep the two astronauts in orbit for longer over fears a trip back on the spacecraft could end in disaster.

During this time, the teams were conducting tests on the issues to determine if capsule could fly.

Last week Boeing said that it 'remains confident in the Starliner spacecraft and its ability to return safely with crew.' 

However, experts told DailyMail.com in June that NASA could be forced to launch a rescue mission, suggesting Elon Musk's SpaceX would be tapped to get it done.

Mike Gruntman, professor of astronautics at the University of Southern California, told DailyMail.com that 'it is more likely that SpaceX would be able to provide an additional launch in the foreseeable future to bring the astronauts back.'

'It is highly unfortunate that Boeing's Starliner, after so much delay with its flight, continues to face problems,' Gruntman continued.

'For decades, Boeing was one of the most admired aerospace and defense companies. It is a true national tragedy.'

Problems with Boeing's commercial jets, including turbulence, mechanical issues and tailstrikes, have cost the company at least $3 billion.

And NASA awarded Boeing a $4.2 billion contract to build Starliner as a taxi for astronauts to the ISS.

A meeting this week of NASA's Commercial Crew Program, which oversees Starliner, ended with some officials disagreeing on a plan to accept Boeing's testing data and use Starliner to bring the astronauts home.

'We didn't poll in a way that led to a conclusion,' Commercial Crew Program chief Steve Stich said.

'We heard from a lot of folks that had concerns, and the decision was not clear,' Ken Bowersox, NASA's space operations chief, added.

While no decision has been made on using Starliner or SpaceX's Crew Dragon, NASA has been buying Boeing more time to do more testing and gather more data to build a better case to trust Starliner.

Sometime next week is when NASA expects to decide, officials said.

Boeing's testing so far has shown that four of Starliner's jets had failed in June because they overheated and automatically turned off, while other thrusters re-fired during tests appeared weaker than normal because of some restriction to their fuel.

Ground tests in late July at the White Sands Missile Range in New Mexico have helped reveal that the thrusters' overheating causes a Teflon seal to warp, choking propellant tubes for the thrusters and thereby weakening their thrust.

'That, I would say, upped the level of discomfort, and not having a total understanding of the physics of what's happening,' Stich said, describing why NASA now appears more willing to discuss a Crew Dragon contingency after previously downplaying such a prospect to reporters.

Starliner took off on June 5 at 10:52am ET from Cape Canaveral Space Force Station in Florida with a leak that forced a scrub in May.

Teams detected a valve leaking helium and scrubbed the mission.

Engineers suspected that the issue came from a defective rubber seal the size of a shirt button, and said that even if the leak worsens, it could be managed in flight - and set the next launch for June 1.

However, Starliner was again plagued with misfortunes when the capsule was automatically halted with minutes to go before liftoff by a computer-abort system.

The postponement was triggered by computers on the Atlas V rocket's launchpad that coordinate the final moments before liftoff, but the Starliner capsule appeared healthy, officials said.

The issues sparked concern among a NASA contractor who urged the American space agency to 're-double safety checks and re-examine safety protocols to make sure the Starliner is safe before something catastrophic happens.'

Erin Faville, president of ValveTech, raised concerns about the June 6 launch, telling DailyMail.com: 'I warned. I will choose to let it play out.'

Starliner has encountered five failures of its 28 maneuvering thrusters, five leaks of helium gas meant to pressurize those thrusters, and a slow-moving propellant valve that signaled unfixed past issues since launching.

When Starliner arrived in the space station's vicinity to dock on June 6, the five thruster failures prevented a close approach by the spacecraft until Boeing made a fix.

Over the past several weeks, Boeing has conducted thruster test firings on the ground and in space to understand why five thrusters failed ahead of Starliner's arrival at the space station.

All but one came back online. Helium leaks in the capsule's propulsion system also cropped up.