The Titanic tourist submersible that vanished on a trip to the 112-year-old shipwreck at the bottom of the Atlantic Ocean has run out of oxygen, according to officials' estimates.
OceanGate Expeditions, which operates the Titan sub and has its CEO Stockton Rush aboard the missing vessel, told the Coast Guard Sunday evening that the vehicle was equipped with only 96 hours of oxygen, with the timer running out around 7:08 a.m. Thursday morning.
The status of the five passengers aboard the ill-fated trip remains unclear as US and Canadian officials work around the clock to attempt to locate the missing Titan sub 900 miles east of Cape Cod.
Along with Rush, who served as the vessel's pilot, the missing include British billionaire Hamish Harding, Pakistani tech and energy mogul Shahzada Dawood and his 19-year-old son Sulaiman, and famed Titanic explorer Paul-Henri Nargeolet.
The US Coast Guard said it received word from OceanGate about the missing submersible eight hours after it lost contact with its mothership, the Polar Prince.
OceanGate said the sub disappeared less than two hours after it submerged Sunday afternoon.
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Unlike a normal submarine, a submersible is unable to get to the bottom of the ocean and back without its mothership, with Titan depending on the Polar Prince for navigation in the depths.
Stuck inside the cramped, 22-foot-long sub, experts agreed that the passengers could've actually shortened their 96 hours of oxygen by panicking.
Mike Tipton, the head of the extreme environments laboratory at the UK's Portsmouth University, told Insider that humans can only go for about three minutes without oxygen.
With a depleting air supply, people can experience restlessness, headaches, confusion, shortness of breath, blue fingertips, increased heart rate and eventually loss of consciousness, the expert said.
More than three minutes without oxygen can lead to brain damage, and eventually death.
Along with the lack of oxygen, Tipton warned that the passengers could've also faced carbon dioxide poisoning inside the sub if its filtration system had been damaged or ran out of power.
The grizzly outcome is among the three major predictions experts agreed would have befallen the tourist group.
Along with acknowledging that the vessel could be stuck underwater on-route to the Titanic shipwreck, which lies 12,500 feet below the surface, the US Coast Guard said it was possible Titan successfully resurfaced but lacked the means to communicate its location.
"If it's on the surface, we're fairly sure we're going to be able to find it," Coast Guard Capt. Jamie Frederick assured reporters Tuesday.
It's unclear how long the passengers would be able to survive adrift in the ocean.
Titanic expedition leader G. Michael Harris previously told the families of the five passengers to prepare for the worst-case scenario, which he predicted was a breach in the Titan's hull.
"Worst situation is something happened to the hull. Our fear is that it imploded at around 3,200 meters," Harris told Fox News.