Two astronauts stranded on International Space Station after major Boeing faults

NASA astronauts Barry "Butch" Wilmore and Suni Williams were launched aboard Starliner on June 5 and arrived at the ISS.

However, their arrival followed a 24-hour flight in which the spacecraft encountered four helium leaks and five failures of its 28 manoeuvring thrusters.

NASA's commercial crew program manager Steve Stich told a news conference the new delay of the return of Starliner is intended "to give our team a little bit more time to look at the data, do some analysis and make sure we're really ready to come home."

Starliner's first flight with astronauts is a crucial last test in a much-delayed and over-budget program before NASA can certify the spacecraft for routine astronaut missions and add a second US crew vehicle to its fleet, alongside SpaceX's Crew Dragon.

Officials from Nasa and Boeing say they plan to analyse the vehicle over the coming days before starting preparations for the return journey.

Stich said: "So far, we don’t see any scenario where Starliner is not going to be able to bring Butch and Suni home."

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The return to Earth is expected to last about six hours and target a location in the desert of Utah, New Mexico or other backup locations, depending on local weather conditions.

The latest in-flight problems follow years of other challenges Boeing has faced with Starliner, including a 2019 uncrewed test failure where dozens of software glitches, design problems and management issues nixed its ability to dock to the ISS. A 2022 repeat uncrewed test had a successful docking.

It comes as Boeing is tangled amid a safety crisis over its 737 Max aeroplanes after a door blew off a flight over Oregon in January, which has led to new scrutiny from regulators.

Boeing’s outgoing chief executive David Calhoun was collared at a US Senate hearing of those killed in two previous incidents in which 737 Max jets crashed. He apologised for their losses but said he was "proud" of the safety record of the company.

Relatives of the victims of two fatal cashes have asked the Justice Department to seek a fine against the company of up to $24.78billion and move forward with a criminal prosecution.

Paul Cassel, a lawyer representing 15 families, wrote in a letter to the Justice Department released earlier today: "Because Boeing’s crime is the deadliest corporate crime in US history, a maximum fine of more than $24billion is legally justified and clearly appropriate.

The two fatal crashes of Boeing 737 MAX planes occurred in 2018 and 2019 in Indonesia and Ethiopia and led to the best-selling plane's worldwide grounding for 20 months. A safety system called MCAS was linked to both fatal crashes.