Oxygen on the missing Titanic submersible is expected to run out in hours, with hopes of finding the five people on board starting to fade.

The vessel, named Titan, 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.

Ships, planes and underwater craft have been deployed to the area with rescuers searching a remote part of the Atlantic Ocean more than twice the size of the US state of Connecticut in waters as deep as 4,020m (13,200ft).

Titanic sub search – live: Oxygen supply dwindling rapidly

The US Coast Guard has been leading an international rescue effort, which was stepped up after underwater noises were heard on Tuesday and again on Wednesday, although experts have been unable to determine the cause of the sounds.

According to OceanGate, Titan’s operator, the 6.7m-long (22ft) OceanGate Expeditions vessel which has British billionaire adventurer Hamish Harding on board, has a 96-hour oxygen supply in case of emergencies.

Also in the undersea craft are British businessman Shahzada Dawood, his son Suleman Dawood, OceanGate’s US-based chief executive and founder Stockton Rush and French submersible pilot Paul-Henri Nargeolet.

A former passenger on one of Titan’s maiden voyages told Sky News on Thursday he ultimately “decided to back off” from the Titanic dive project as he “couldn’t get comfortable with the design”.

US explorer Josh Gates described how there were system errors during his journey on the submersible in a “shakedown dive” in 2021 with Mr Rush.

“I would say that some of the systems on board performed very well. Some of them didn’t perform well at all. We had issues with thrusters, we had issues with computer control aboard,” he said.

Key points:
• Mission to find vessel enters a new phase of urgency with the final few hours of oxygen left on board
• OceanGate’s US-based chief executive Stockton Rush, French submersible pilot Paul-Henri Nargeolet and Britons – billionaire adventurer Hamish Harding, businessman Shahzada Dawood, and his son Suleman Dawood are on the sub
• The US coast guard is leading an international rescue effort, with a vast area of the Atlantic Ocean off the Canadian coastline being searched
• Rescuers have rushed more ships, planes and vessels to the site of the disappearance, hoping underwater sounds they have been detecting for days might help narrow their search

No other sub like Titan in the world

The US Coast Guard predicts the oxygen supply in the Titan submersible will run out at 12.08pm UK time today.

An extensive search and rescue operation is continuing, as those involved say they will “hold on hope until the very end”.

One of the vessels sent to help search efforts is French research vessel L’Atalante which carries a remotely operated vehicle (ROV), Victor 6000.

It has the capability to lift the Titan ship to the surface.

Asked whether the mission was changing to become a recovery search, Captain Jamie Frederick of the US Coast Guard told reporters: “This is a search and rescue mission, 100%, we are smack dab in the middle of search and rescue and will continue to put every available asset that we have in an effort to find the Titan and the crew members.”

Even those who have expressed optimism have warned many obstacles remain: from pinpointing Titan’s location, to reaching it with rescue equipment, then bringing it to the surface – assuming it is still intact.

All this has to happen before the passengers’ oxygen supply runs out.

Read more:
Passenger who took 2021 trip to see Titanic says sub ‘was not safe’
Fate of missing Titan submersible’s passengers may rest on one man

Number of ‘unknowns and mysteries’ about sub

There is no other vehicle like Titan anywhere in the world – it is a one-off, said Mr Gates.

He said Titan is described in the waivers as an “experimental craft” and added “it is truly experimental in a very real sense of the word”.

“It is like being a test pilot on a plane that has never ever flown before, and so there is a totally different category of risk with a vehicle like this,” he said.

“There are a huge number of unknowns with a submersible like this… You have an innovative, novel design, but it comes with a lot of mysteries in terms of how it is going to perform over time.”

Mr Gates said the fact that Titan apparently has not surfaced despite being “well off the bottom” when contact was lost at the weekend opens up questions over what else may have gone wrong.

One such possibility is a hull failure, which “speaks to the carbon fibre design of Titan”, Mr Gates said.

He added that though the time period for a rescue is closing, “we should remain hopeful here for a positive outcome for this”.

Mr Gates also touched on some online criticism of the passengers for boarding the experimental craft at a high cost, saying there have been “a lot of callous comments”.

He said Titanic has “fascinated the world” since she sank a century ago and the shipwreck holds “a real fascination for people”.

“It takes a lot of courage and determination to go on a voyage like this,” he said, adding that he “commended” the five men aboard Titan for having the “passion and determination” to embark on the deep-sea trek.