The missing tourist submersible, which had five persons on board, including British billionaire Hamish Harding, is believed to have last ‘pinged’ while it was directly above the Titanic, where it was headed.

As part of their £195,000 per person tour of the 1912 wreckage, the sub, owned and operated by OceanGate Expeditions, was transporting a crew of five persons, including business CEO Stockton Rush, French explorer PH Nargeolet, and Harding, 12,500 feet underwater.

The crew has enough air to survive underwater until 12pm on Thursday UK time (7am EST), despite having launched at roughly 4am on Sunday but losing contact with the sub’s mothership MV Polar Prince one hour and 45 minutes into the two-hour descent.

Also Read: Who is Stockton Rush, founder of OceanGate Expeditions on board missing Titanic submersible?

Rescuers acknowledged that the sub may have become caught in the Titanic wreckage, which is 370 miles from Newfoundland in Canada but is located in US seas, as the grim race against time got underway yesterday afternoon.

Submarine experts worry that the ship is too deep for manned rescue subs, such as the US Navy sub, which can only go up to 2,000 feet, and that the only viable option for getting there may be a remotely operated vehicle. These have a 20,000-foot depth limit.

Also Read: Who is Paul-Henry Nargeolet, French submersible pilot on board missing Titanic submarine

The Titanic submarine, called “Titan,” lost communication with the surface for at least seven hours despite appearing to be getting closer to its destination.

The Polar Prince receives pings from Titan every 15 minutes, the latest of which was at approximately 10 a.m. EST, while the submersible drifted above the Titanic ruins.

Chaos started to spread at that same time. At 9 o’clock in the evening, a distress call was sent to the US Coast Guard, whose Boston branch is in charge of organizing what would be the deepest underwater rescue mission ever.