The Titan submersible.Photo:Alamy Stock Photo

The Oceangate submersible Titan

Alamy Stock Photo

The missingTitansubmersible is due to run out of air this morning.

According to BBC News, the sub’s breathing air supply is expected to run out Thursday, June 22, at around 6:00 a.m. EST. The vessel had about 96 hours of oxygen onboard when its dive began on Sunday, United States Coast Guard officials said,according to CBS.

The U.S. Coast Guard admiral leading the search for theTitantold the BBCon Wednesday that the search team is operating under the assumption that they have around 20 hours left to find the sub.“One of the factors that makes it hard to predict how much oxygen is left is that we do not know the rate of the consumption of oxygen per occupant on the sub,” Rear Admiral John Mauger told BBC while speaking of the vessel, which was traveling to the wreckage of theTitanicwhen it went missing.

Mauger also told the outlet that he and his team had spoken to thefive passengers' families directly about their search efforts.

An OceanGate submersible.Ocean Gate / Handout/Anadolu Agency via Getty Images

An undated photo shows tourist submersible belongs to OceanGate begins to descent at a sea. Search and rescue operations continue by US Coast Guard in Boston after a tourist submarine bound for the Titanic’s wreckage site went missing off the southeastern coast of Canada

Ocean Gate / Handout/Anadolu Agency via Getty Images

Coast Guard Capt. Jamie Frederick said during a press conference on Tuesday afternoon that the vessel had"about 40 hours of breathable air left" based on the estimate that it had 96 hours of available oxygen when it was sealed.

The sub is carrying five passengers and first went missing on Sunday, June 18,according to the First Coast Guard District’s official Twitter account. Per the BBC, contact withTitanwas lost on Sunday as it made a more than two-mile descent to theTitanicwreckage site in the North Atlantic.

The search for theTitanbegan shortly after they “lost all communication” with Canadian expedition vessel Polar Prince “approximately 1 hour and 45 minutes” into the dive on Sunday, Frederick said.

U.S. Coast Guard Rear Admiral John Mauger.AP Photo/Steven Senne

U.S. Coast Guard Rear Adm. John Mauger, commander of the First Coast Guard District

AP Photo/Steven Senne

Joe MacInnis, a renowned diver who has made two trips to the wreck of the Titanic,told CNNon Wednesday that the five passengers in the sub would be “resting, breathing as little as possible, and trying to keep calm” in order to conserve their energy.

“It’s a target, it’s a focus for us to look at,” Rear Admiral John Mauger toldCBS Morningsof the noises, though he added, “We don’t know the source of that noise."

The sub was traveling to the wreckage site of the Titanic.Ocean Gate/Handout/Anadolu Agency/Getty

An undated photo shows tourist submersible

Ocean Gate/Handout/Anadolu Agency/Getty

“This is an incredibly complex case,” Mauger continued when asked if he was optimistic about the rescue mission.

“As long as there is an opportunity for survival, we will continue to work and bring every resource to bear on the search,” he added.

The noises detected in the water have been described as “banging noises” per CNN. However, on Wednesday morning, theU.S. Coast Guard denied hearing the noises.

“We don’t have anything at this time indicating any implosion or banging,” U.S. Coast Guard Petty Officer 3rd Class (PO3) Briana Carter tells PEOPLE

Paul-Henry Nargeolet Hamish Harding Stockton Rush.EVARISTO SA/AFP via Getty; Victoria Sirakova/Getty;  OceanGate

Paul-Henry Nargeolet Hamish Harding Stockton Rush

EVARISTO SA/AFP via Getty; Victoria Sirakova/Getty;  OceanGate

Chris Brown, an explorer and friend of one of the passengers,told the BBChe believed the noises could have come from the sub.

“If you made a continuous noise, that’s not going to get picked up, but doing it every 30 minutes, that suggests humans,” he said. “I’m sure they’re all conserving oxygen and energy, because it’s cold and dark down there.”

Aboard the sub was OceanGate CEO Stockton Rush, who was piloting the voyage; British-Pakistani businessman Shahzada Dawood and his 19-year-old son Suleman Dawood; and British billionaire Hamish Harding. FrenchTitanicexpert Paul-Henri Nargeolet was also aboard, PEOPLE has confirmed.

Shahzada Dawood.SETI Institute

Shahzada Dawood

SETI Institute

Nargeolet, known as PH, is a retired French diver with Navy experience. Submarine search and rescue expert Frank Owen told the BBC on Wednesday that Nargeolet would know what to do in this situation.

“On board this craft is a retired French navy diver,” he said, per the BBC. “He would know the protocol for trying to alert searching forces… on the hour and the half hour you bang like hell for three minutes.”

Passenger Hamish Harding’s friend Terry Virts.Alex J. Berliner/ABImages via AP Images

Terry Virts attends the Cinema Audio Society Awards

Alex J. Berliner/ABImages via AP Images

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“Hey, we’re headed out tomorrow, it looks good, the weather’s been bad so they’ve been waiting for this,” the 58-year-old billionaire wrote, according to Virts, who said his pal undoubtedly “understood the risks” of the mission to explore the wreck, thePostreports.

“We talked quite a bit about the risks and the different things that they were going to be able to do,” Virts explained on the program, per thePost. “So he was very excited about it.”

source: people.com