International teams of rescuers led by the US Coast Guard were scouring a vast patch of the remote North Atlantic for a third day on Tuesday, racing against time to find a missing submersible before its air supply ran out.
Follow the latest news on the missing Titanic sub here
The US Coast Guard and its Canadian counterpart said the submersible that went missing on Sunday as it was descending to view the wreck of the RMS Titanic had about 40 hours of air left.
Authorities are scouring a 20,000-square-kilometre area as they search for the Titan, a submersible craft that was carrying four wealthy tourists and a pilot when it disappeared on Sunday.
Capt Jamie Frederick of the US Coast Guard gave a brief update on Tuesday in Boston, saying the submersible had about 40 hours of air left, meaning it would run out by early on Thursday morning.
“This is a very complex search and the unified team is working round the clock to bring all available assets and expertise to bear as quickly as possible in an effort to solve this very complex problem,” Capt Frederick said.
The Titanic site is about 1,450km east of Cape Cod and 644km south of St John's, Newfoundland.
US and Canadian aircraft have searched an area larger than the state of Connecticut, Capt Frederick said. New York Air National Guard has also sent members the help the search.
France has sent a research vessel with an underwater robot that could potentially reach the site of the sunken submersible.
The Canadian military has dropped sonar buoys to listen for any sounds that might be coming from the Titan and a commercial vessel with an unmanned vehicle capable of deep dives was also searching near the site, Capt Frederick said, but search efforts have come up empty so far.
Those aboard the submersible, the highlight of a tourist expedition that costs $250,000 per person, included British billionaire Hamish Harding, 58, who lives in Dubai, and Pakistani-born businessman Shahzada Dawood, 48, with his 19-year-old son Suleman, who are both British citizens.
The 77-year-old French explorer Paul-Henri Nargeolet and Stockton Rush, founder and chief executive of the vessel's US-based operating company OceanGate Expeditions, were also reported to be on board. Authorities have not confirmed the identity of any passenger.
A retired US Coast Guard captain has described the difficulties search and rescue crews face.
“I can guarantee that they are scouring the globe for assets that are capable of even operating at the depths where the Titanic is,” Andrew Norris, who retired in 2016 after 26 years of active duty, told The National.
The biggest challenge is that even if Titan is located on the ocean floor, there are no vessels in existence that can transfer the passengers, so any sort of sub-to-sub rescue is impossible.
The wreck of the Titanic, which sank on its maiden voyage in 1912, lies at a depth of 3,800 metres, where it is pitch black and water pressure is nearly 400 times greater than at the surface.
He said the only hope for the tourist submersible is if the pilot is somehow able to untangle the vessel from whatever might be pinning it underwater – if that is what is happening.
“That's all that strikes me as a realistic chance. It's a very, very, very, very slim chance. But to me, that's the only one that's even feasible,” he said.
The Titanic wreck is located roughly 700km off the coast of Newfoundland, Canada.
The US Coast Guard is likely to conduct an aerial search of the area as well as use underwater sonar to search for the missing vessel.
“If it's on the surface the procedures are well known and well honed,” said Mr Norris. “If it's not, then you're left with an underwater search and that's completely sort of out of the coastguard's wheelhouse.”
