A former passenger on the missing submersible that visited the Titanic wreck has said he has 'no idea' how the crew is going to get back to the surface.
Five people including British Billionaire Hamish Harding are currently missing after the OceanGate vessel went missing yesterday afternoon.
He is one of the mission specialists on the five-person that is believed to be about 435 miles south of St John's, Newfoundland in the US.
The other four members of the crew were identified earlier this morning.
A major search and rescue operation, which is being led by the US Coast Guard and involving military aircraft 900 miles east of Cape Cod, was continuing today.
However former crew member, Mike Reiss, who took part in a dive to the wreckage last year has said he's 'not optimistic' about the passengers returning.
He told BBC Breakfast: 'I'm not optimistic, because I know the logistics of it and how vast the ocean is.
'It's meant to go down further than any other vessel, so the idea that if it is down at the bottom I've got no idea how anyone is going to be able to access it let alone bring it back up.
'I did three separate dives, and every time they lost communication.
'This is not saying it is a shoddy ship, it is just all new technology and they are learning it as they go along.'
A search and rescue mission is taking place in the north Atlantic Ocean after coastguards lost contact with the 21-foot vessel.
It is one of a number that occasionally take tourists, experts and scientists down to see the world-famous shipwreck.
It can reportedly take eight hours for a submersible to take people down to the wreck - which lies 13,000ft below the surface of the ocean - and back up again, as part of a multi-day trip.
Last year, it was reported that one such excursion run by OceanGate cost a group of guests $250,000.
The mission was 10 days long, with eight of those days at sea, according to a tourist brochure.
According to the vessel's operator there is a maximum oxygen supply of 96 hours in case of emergencies, meaning that only approximately two days of 'life support' remain.
OceanGate Expeditions said its focus was on those aboard the vessel and their families.
'We are deeply thankful for the extensive assistance we have received from several government agencies and deep sea companies in our efforts to re-establish contact with the submersible,' the company said in a statement.
'We are working toward the safe return of the crew members.'
The US Coast Guard said the Canadian research vessel Polar Prince and 106 Rescue wing will continue to conduct surface searches while the US Coast Guard sent two C-130 flights to search for the missing submersible.
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