A former Royal Navy submarine captain described the outlook for the missing Titan submersible as "bleak" as the oxygen deadline passes. While the search-and-rescue operation continues for Titan, oxygen is thought to have run out aboard the submersible.
The sub lost contact with its mothership on Sunday morning. It had around 96 hours of oxygen on board and, as of Thursday lunchtime, that amount of time has now passed.
Ryan Ramsey told the PA news agency: "The outlook is bleak, that's the only word for it, as this tragic event unfolds and almost the closing stages of where this changes from rescue to a salvage mission. That doesn't mean to say that the current ships and forces deployed won't continue to keep looking.
"They won't stop for many days, I imagine, but the reality is if you base it off oxygen alone, then they're out of oxygen. Carbon dioxide is also a critical element to it as well as the cold. It would be a miracle if there were survivors from it."
The vessel lost communication with tour operators on Sunday while about 435 miles south of St John’s, Newfoundland, during a voyage to the Titanic shipwreck off the coast of Canada. The 6.7m (22ft)-long OceanGate Expeditions vessel is said to have had a 96-hour oxygen supply in case of emergencies.
On board the undersea craft when it set off were British billionaire adventurer and founding member of the Board of Trustees of The Explorers Club, Hamish Harding; UK-based businessman Shahzada Dawood and his son Suleman Dawood; OceanGate’s chief executive and founder Stockton Rush and as well as French submersible pilot Paul-Henri Nargeolet.
Meanwhile Downing Street said on Thursday that a British submariner and equipment from a UK firm would help the search.
A No 10 spokesman said: "At the request of US Coastguard the UK has embedded a Royal Navy submariner to assist the search and rescue effort for the missing submarine. That is Lieutenant Commander Richard Kantharia."
Lt Cmdr Kantharia "has significant knowledge of submarine warfare and dived operations and so he will obviously be bringing that experience to the search and rescue team". The officer was on exchange with the US Navy and has been seconded to the search and rescue team. A British C-17 aircraft will transport "specialist commercial equipment" provided by Magellan to St John's to assist with the search-and-rescue effort.
Downing Street said Lt Cmdr Kantharia would be part of the Titan rescue efforts "as long as is required". The experienced submariner is understood to have joined the US Coastguard mission on Tuesday evening in the US.
A spokesman for Prime Minister Rishi Sunak, asked whether the request for UK assistance should have come sooner, said: "We've always said we stand ready to provide any assistance required and that continues to be the case. The search and rescue efforts continue and we will look to support that in any way we can."
Asked how long Lt Cmdr Kantharia would be "embedded" with the rescue efforts, the spokesman replied: "As long as is required." The No 10 official, asked whether Mr Sunak planned to speak to the families of the British people onboard the missing Titanic submersible, said the Prime Minister's "thoughts remain with" them and that the Foreign Office is in "constant contact" with those affected.