The frantic search for the missing Titanic submersible is now in in its final half an hour with regards to the projected 96 hours of emergency oxygen available to the five explorers. The only vessel capable of completing the rescue mission is now thought to have arrived and joined the search.
The huge operation has until lunchtime today (Thursday, June 22) to locate the sub called Titan, get it back to the surface - and save the lives of the five people onboard. Last night, US Coast Guards calculated that Titan's oxygen will run out at 7.08am today, 12.08 BST.
There had been a glimmer of hope after tapping noises - described by experts as 'likely signs of life' - had been heard on Tuesday and again on Wednesday. However, the US Coast Guard said it could not confirm what the banging noises picked up by a surveillance plane were.
And, last night, a former US Navy nuclear submarine commander explained why he does not think the noises are from the missing vessel. And a former Royal Navy submariner said he thinks the five people on board the missing Titanic submersible may already be dead - and finding the lost sub could take months.
Nonetheless, the search efforts for missing men are intensifying - with just hours remaining to save them. The surface search extends across an area twice the size of Connecticut.
And a former US Navy diver believes there is still cause for optimism as the search for the missing Titanic tourist submersible continues. Meanwhile, Atlante - a French vessel carrying the only underwater vehicle able to rescue those trapped on the Titan - is believed to have entered the search.
Marine traffic trackers show it has joined forces with specialist tugs and craft, to the north of the Titan's mothership, Polar Prince.
Hopes of finding the sub rest on Atlante's Victor 6000, which can reach depths of 20,000ft. More than 10,000 square miles of the Atlantic Ocean around the Titanic wreckage, roughly 400 miles off the eastern Canadian coast, have been trawled by planes, submarines and explorers in a concerted international effort to fund the explorers.
The Coast Guard statement came after Rolling Stone, citing what it described as internal US Department of Homeland Security emails on the search, said that teams heard "banging sounds in the area every 30 minutes."
In underwater disasters, a crew unable to communicate with the surface relies on banging on their submersible's hull to be detected by sonar. However, no official has publicly suggested that's the case and noises underwater can come from a variety of sources.
Yet the reports have sparked hope in some, including Richard Garriott de Cayeux, the president of The Explorers Club. He wrote an open letter to his club's adventurers, who include the missing British man and the Titanic expert aboard the Titan, that they had "much greater confidence" now after they spoke to officials in Congress, the US military and the White House about the search.
Three C-17 transport planes from the US military have been used to move commercial submersibles and support equipment from Buffalo, New York, to St. John's, Newfoundland, to aid in the search, a spokesperson for US Air Mobility Command said.
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