Human remains have likely been recovered from the wreckage of the submersible that imploded during an underwater voyage to view the Titanic, the U.S. Coast Guard said Wednesday.The news came hours after the announcement that debris from the Titan, collected from the seafloor more than 12,000 feet below the surface of the North Atlantic, had arrived in St. John's, Newfoundland. Twisted chunks of the submersible were unloaded at a Canadian Coast Guard pier.Recovering and scrutinizing the wreckage is a key part of the investigation into why the Titan imploded last week, killing all five people on board. The multi-day search and eventual recovery of debris from the 22-foot vessel captured the world's attention."There is still a substantial amount of work to be done to understand the factors that led to the catastrophic loss of the Titan and help ensure a similar tragedy does not occur again,” Coast Guard Chief Capt. Jason Neubauer said in a statement released late Wednesday afternoon.The “presumed human remains” will be brought to the United States, where medical professionals will conduct a formal analysis, Neubauer said. He added that the Coast Guard has convened an investigation of the implosion at the highest level. The Marine Board of Investigation will analyze and test evidence, including pieces of debris, at a port in the U.S. The board will share the evidence at a future public hearing whose date has not been determined, the Coast Guard said.Neubauer said the evidence will provide “critical insights" into the cause of the implosion.Debris from the Titan, which is believed to have imploded on June 18 as it made its descent, was located about 12,500 feet underwater and roughly 1,600 feet from the Titanic on the ocean floor. The Coast Guard is leading the investigation, in conjunction with several other government agencies in the U.S. and Canada.Authorities have not disclosed details of the debris recovery, which could have followed several approaches, according to Carl Hartsfield, who directs a lab at the Woods Hole Oceanographic Institution that designs and operates autonomous underwater vehicles and has been serving as a consultant to the Coast Guard.“If the pieces are small, you can collect them together and put them in a basket or some kind of collection device," Hartsfield said Monday. Bigger pieces could be retrieved with a remote-operated vehicle, or ROV, such as the one brought to the wreckage site by the Canadian ship Horizon Arctic to search the ocean floor. For extremely big pieces, a heavy lift could be used to pull them up with a tow line, he said.Representatives for Horizon Arctic did not respond to requests for comment. The ROV's owner, Pelagic Research Services, a company with offices in Massachusetts and New York, is “still on mission” and cannot comment on the investigation, company spokesperson Jeff Mahoney said Wednesday.“They have been working around the clock now for 10 days, through the physical and mental challenges of this operation,” Mahoney said.Analyzing the recovered debris could reveal important clues about what happened to the Titan, and there could be electronic data recorded by the submersible’s instruments, Hartsfield said."So the question is, is there any data available? And I really don’t know the answer to that question,” he said Monday.The Transportation Safety Board of Canada, which is conducting a safety investigation into the Titan's Canadian-flagged mother ship, the Polar Prince, said Wednesday that it has sent that vessel’s voyage data recorder to a lab for analysis.Stockton Rush, the Titan's pilot and CEO of OceanGate Expeditions, the company that owned the submersible, was killed in the implosion along with two members of a prominent Pakistani family, Shahzada Dawood and his son Suleman Dawood; British adventurer Hamish Harding; and Titanic expert Paul-Henri Nargeolet.OceanGate is based in the U.S. but the submersible was registered in the Bahamas.The company charged passengers $250,000 each to participate in the voyage. The implosion of the Titan has raised questions about the safety of private undersea exploration operations. The Coast Guard wants to use the investigation to improve the safety of submersibles.___Associated Press writers Holly Ramer in Concord, New Hampshire, and Michael Casey in Boston contributed to this report.

PORTLAND, Maine —

Human remains have likely been recovered from the wreckage of the submersible that imploded during an underwater voyage to view the Titanic, the U.S. Coast Guard said Wednesday.

The news came hours after the announcement that debris from the Titan, collected from the seafloor more than 12,000 feet below the surface of the North Atlantic, had arrived in St. John's, Newfoundland. Twisted chunks of the submersible were unloaded at a Canadian Coast Guard pier.

Recovering and scrutinizing the wreckage is a key part of the investigation into why the Titan imploded last week, killing all five people on board. The multi-day search and eventual recovery of debris from the 22-foot vessel captured the world's attention.

"There is still a substantial amount of work to be done to understand the factors that led to the catastrophic loss of the Titan and help ensure a similar tragedy does not occur again,” Coast Guard Chief Capt. Jason Neubauer said in a statement released late Wednesday afternoon.

The “presumed human remains” will be brought to the United States, where medical professionals will conduct a formal analysis, Neubauer said. He added that the Coast Guard has convened an investigation of the implosion at the highest level. The Marine Board of Investigation will analyze and test evidence, including pieces of debris, at a port in the U.S. The board will share the evidence at a future public hearing whose date has not been determined, the Coast Guard said.

Neubauer said the evidence will provide “critical insights" into the cause of the implosion.

Paul Daly/The Canadian Press/AP

Debris from the Titan, which is believed to have imploded on June 18 as it made its descent, was located about 12,500 feet underwater and roughly 1,600 feet from the Titanic on the ocean floor. The Coast Guard is leading the investigation, in conjunction with several other government agencies in the U.S. and Canada.

Authorities have not disclosed details of the debris recovery, which could have followed several approaches, according to Carl Hartsfield, who directs a lab at the Woods Hole Oceanographic Institution that designs and operates autonomous underwater vehicles and has been serving as a consultant to the Coast Guard.

“If the pieces are small, you can collect them together and put them in a basket or some kind of collection device," Hartsfield said Monday. Bigger pieces could be retrieved with a remote-operated vehicle, or ROV, such as the one brought to the wreckage site by the Canadian ship Horizon Arctic to search the ocean floor. For extremely big pieces, a heavy lift could be used to pull them up with a tow line, he said.

Representatives for Horizon Arctic did not respond to requests for comment. The ROV's owner, Pelagic Research Services, a company with offices in Massachusetts and New York, is “still on mission” and cannot comment on the investigation, company spokesperson Jeff Mahoney said Wednesday.

“They have been working around the clock now for 10 days, through the physical and mental challenges of this operation,” Mahoney said.

Analyzing the recovered debris could reveal important clues about what happened to the Titan, and there could be electronic data recorded by the submersible’s instruments, Hartsfield said.

"So the question is, is there any data available? And I really don’t know the answer to that question,” he said Monday.

The Transportation Safety Board of Canada, which is conducting a safety investigation into the Titan's Canadian-flagged mother ship, the Polar Prince, said Wednesday that it has sent that vessel’s voyage data recorder to a lab for analysis.

Stockton Rush, the Titan's pilot and CEO of OceanGate Expeditions, the company that owned the submersible, was killed in the implosion along with two members of a prominent Pakistani family, Shahzada Dawood and his son Suleman Dawood; British adventurer Hamish Harding; and Titanic expert Paul-Henri Nargeolet.

OceanGate is based in the U.S. but the submersible was registered in the Bahamas.

The company charged passengers $250,000 each to participate in the voyage. The implosion of the Titan has raised questions about the safety of private undersea exploration operations. The Coast Guard wants to use the investigation to improve the safety of submersibles.

___

Associated Press writers Holly Ramer in Concord, New Hampshire, and Michael Casey in Boston contributed to this report.

When millionaire Steve Fossett's plane went missing over the Nevada range in 2007, the swashbuckling adventurer had already been the subject of two prior emergency rescue operations thousands of miles apart.That prompted a prickly question: After a sweeping search for the wealthy risktaker ended, who should foot the bill?Video above: What went wrong? Search for answers in Titanic sub implosionIn recent days, the massive hunt for a submersible vehicle lost during a North Atlantic descent to explore the wreckage of the Titanic has refocused attention on that conundrum. And with rescuers and the public fixated first on saving and then on mourning those aboard, it has again made for uneasy conversation."Five people have just lost their lives and to start talking about insurance, all the rescue efforts and the cost can seem pretty heartless — but the thing is, at the end of the day, there are costs," said Arun Upneja, dean of Boston University's School of Hospitality Administration and a researcher on tourism."There are many people who are going to say, 'Why should the society spend money on the rescue effort if (these people) are wealthy enough to be able to ... engage in these risky activities?'"That question is gaining attention as very wealthy travelers in search of singular adventures spend big to scale peaks, sail across oceans and blast off for space.The U.S. Coast Guard declined Friday to provide a cost estimate for its efforts to locate the Titan, the submersible investigators say imploded not far from the world's most famous shipwreck. The five people lost included a billionaire British businessman and a father and son from one of Pakistan's most prominent families. The operator charged passengers $250,000 each to participate in the voyage."We cannot attribute a monetary value to Search and Rescue cases, as the Coast Guard does not associate cost with saving a life," the agency said.While the Coast Guard's cost for the mission is likely to run into the millions of dollars, it is generally prohibited by federal law from collecting reimbursement related to any search or rescue service, said Stephen Koerting, a U.S. attorney in Maine who specializes in maritime law.But that does not resolve the larger issue of whether wealthy travelers or companies should bear responsibility to the public and governments for exposing themselves to such risk."This is one of the most difficult questions to attempt to find an answer for," said Pete Sepp, president of the National Taxpayers Union, noting scrutiny of government-funded rescues dating back to British billionaire Richard Branson's hot air balloon exploits in the 1990s."This should never be solely about government spending, or perhaps not even primarily about government spending, but you can't help thinking about how the limited resources of rescuers can be utilized," Sepp said.The demand for those resources was spotlighted in 1998 when Fossett's attempt to circle the globe in a hot air balloon ended with a plunge into the ocean 500 miles off Australia. The Royal Australian Air Force dispatched a Hercules C-130 transport aircraft to find him. A French military plane dropped a 15-man life raft to Fossett before he was picked up by a passing yacht.Critics suggested Fossett should pay the bill. He rejected the idea.Late that same year the US Coast Guard spent more than $130,000 to rescue Fossett and Branson after their hot air balloon dropped into the ocean off Hawaii. Branson said he would pay if the Coast Guard requested it, but the agency didn't ask.Nine years later, after Fossett's plane vanished over Nevada during what should have been a short flight, the state National Guard launched a months-long search that turned up the wreckage of several other decades-old crashes without finding the millionaire.The state said the mission had cost taxpayers $685,998, with $200,000 covered by a private contribution. But when the administration of Gov. Jim Gibbons announced that it would seek reimbursement for the rest, Fossett's widow balked, noting she had spent $1 million on her own private search.Video below: Maryland man mourning after friend died on OceanGate submersible"We believe the search conducted by the state of Nevada is an expense of government in the performance of government action," a lawyer wrote on behalf of the Fossett estate.Risky adventurism is hardly unique to wealthy people.The pandemic drove a surge in visits to places like national parks, adding to the popularity of climbing, hiking and other outdoor activities. Meanwhile, the spread of cell phones and services has left many feeling that if things go wrong, help is a call away.Some places have laws commonly referred to as "stupid motorist laws," in which drivers are forced to foot the emergency response bill when they ignore barricades on submerged roads. Arizona has such a law, and Volusia County in Florida, home to Daytona, enacted similar legislation this week. The idea of a similar "stupid hiker law" is a regularly debated item in Arizona as well, with so many unprepared people needing to be rescued in stifling triple-digit heat.Most officials and volunteers who run search efforts are opposed to charging for help, said Butch Farabee, a former ranger who participated in hundreds of rescue operations at the Grand Canyon and other national parks and has written several books on the subject.Searchers are concerned that if they did charge to rescue people "they won't call for help as soon as they should and by the time they do it's too late," Farabee said.The tradeoff is that some might take that vital aid for granted. Farabee recounts a call in the 1980s from a lawyer who underestimated the effort needed to hike out of the Grand Canyon. The man asked for a helicopter rescue, mentioning that he had an important meeting the following day. The ranger rejected that request.But that is not an option when the lives of adventurers, some of them quite wealthy, are at extreme risk.At Mount Everest, it can cost tens of thousands of dollars in permit and expedition fees to climb. A handful of people die or go missing while hiking the mountain every year — prompting an emergency response from local officials.While the government of Nepal requires that climbers have rescue insurance, the scope of rescue efforts can vary widely, with Upneja estimating that some could cost "multiple dozens of thousands of dollars."Nepal's Ministry of Foreign Affairs did not respond to a message seeking comment.On the high seas, wealthy yachtsmen seeking speed and distance records have also repeatedly required rescue when their voyages run astray.When the yacht of Tony Bullimore, a British millionaire on a round-the-world journey, capsized 1,400 miles off the Australia Coast in 1997 it seemed he might be done for. Clinging to the inside of the hull, he ran out of fresh water and was almost out of air.When a rescue ship arrived, he swam desperately toward the surface.'I was starting to look back over my life and was thinking, 'Well, I've had a good life, I've done most of the things I had wanted to," Bullimore said afterward. "If I was picking words to describe it, it would be a miracle, an absolute miracle.'Australian officials, whose forces rescued a French yachtsman the same week, were more measured in their assessment."We have an international legal obligation," Ian McLachlan, the defense minister said. "We have a moral obligation obviously to go and rescue people, whether in bushfires, cyclones or at sea."Less was said, however, about the Australian government's request to restrict the routes of yacht races — in hopes of keeping sailors to areas where they might require less rescuing.___Associated Press writer David Sharp in Portland, Maine contributed to this story.

The cost of the unprecedented search for the missing Titan submersible will easily stretch into the millions of dollars, experts said Friday.The massive international effort by aircraft, surface ships and deep-sea robots began Sunday when the Titan was reported missing. Searchers raced against a 96-hour clock in the desperate hope to find and rescue the vessel's occupants before their oxygen supply ran out.But all hope was extinguished Thursday when officials announced the submersible had suffered a catastrophic implosion, killing all five aboard.A scaled-back search remained in place Friday as the robots — remotely operated vehicles, known as ROVs — continued to scan the sea floor for evidence that might shed light on what occurred in the deep waters of the North Atlantic.The search area spanned thousands of miles — twice the size of Connecticut and in waters 2 1/2 miles deep — with agencies such as the U.S. Coast Guard, the Canadian Coast Guard, U.S. Navy and other agencies and private entities.Video below: Former Navy submersible pilot on what could cause cause 'catastrophic implosion'There’s no other comparable ocean search, especially with so many countries and even commercial enterprises being involved in recent times, said Norman Polmar, a naval historian, analyst and author based in Virginia.The aircraft, alone, are expensive to operate, and the Government Accountability Office has put the hourly cost at tens of thousands of dollars. Turboprop P-3 Orion and jet-powered P-8 Poseidon sub hunters, along with C-130 Hercules, were all utilized in the search.Some agencies can seek reimbursements. But the U.S. Coast Guard — whose bill alone will hit the millions of dollars — is generally prohibited by federal law from collecting reimbursement pertaining to any search or rescue service, said Stephen Koerting, an attorney in Maine who specializes in maritime law.“The Coast Guard, as a matter of both law and policy, does not seek to recover the costs associated with search and rescue from the recipients of those services,” the Coast Guard said Friday in a statement.Video below: Friends of lost crew react after debris from sub identifiedThe first priority in search and rescue is always saving a life, and search and rescue agencies budget for such expenses, said Mikki Hastings, president and CEO of the National Association for Search and Rescue.“In the end, these people were in distress. We know what the ultimate result was. But during the search operation, there are people who are in distress,” she said of the Titan submersible.Rescue agencies don’t want people in distress to be thinking about the cost of a helicopter or other resources when a life is in danger.“Every person who is missing – they deserve to be found. That’s the mission regardless of who they are,” she said.

Authorities turned their focus to determining why a submersible carrying people to the wreck of the Titanic imploded deep in the North Atlantic, as tributes poured in for the five aboard who were killed.The announcement that no one survived Thursday brought a tragic end to a five-day saga that included an urgent around-the-clock search for the vessel known as the Titan.The investigation into what happened was already underway and would continue in the area around Titanic where debris from the submersible was found, said Rear Adm. John Mauger, of the First Coast Guard District.“I know there are also a lot of questions about how, why and when did this happen. Those are questions we will collect as much information as we can about now,” Mauger said, adding that it was a “complex case” that happened in a remote part of the ocean and involved people from several different countries.The first hint of a timeline came Thursday evening when a senior U.S. Navy official said that after the Titan was reported missing Sunday, the Navy went back and analyzed its acoustic data and found an “anomaly” that was consistent with an implosion or explosion in the general vicinity of where the vessel was operating when communications were lost. The official spoke on condition of anonymity to discuss a sensitive acoustic detection system.Those killed were Stockton Rush, the CEO of OceanGate Expeditions, the company that owned and operated the submersible; two members of a prominent Pakistani family, Shahzada Dawood and his son Suleman Dawood; British adventurer Hamish Harding; and Titanic expert Paul-Henri Nargeolet.Video below: Friends of lost crew react after debris from sub identifiedThe Titan launched at 6 a.m. Sunday, and was reported overdue Sunday afternoon about 435 miles south of St. John’s, Newfoundland. Rescuers rushed ships, planes and other equipment to the site of the disappearance.Any sliver of hope that remained for finding the crew alive was wiped away early Thursday, when the submersible’s 96-hour supply of air was expected to run out and the Coast Guard announced that debris had been found roughly 1,600 feet from the Titanic.“The debris is consistent with the catastrophic loss of the pressure chamber,” Mauger said.The Coast Guard said Thursday that the sounds detected during the search — that had given rescuers some hope that maybe the people were alive — were likely generated by something other than the Titan.The Navy official who spoke of the “anomaly” heard Sunday said the Navy passed on the information to the Coast Guard, which continued its search because the data was not considered definitive.Tributes to and praise for the searchers who tried to save them poured in from across the globe.Harding’s family said in a statement: ”He was one of a kind and we adored him... What he achieved in his lifetime was truly remarkable and if we can take any small consolation from this tragedy, it’s that we lost him doing what he loved.”Video below: Former Navy submersible pilot on what could cause cause 'catastrophic implosion'In a statement beginning with a Quranic verse, the Dawood family thanked rescuers: “Their untiring efforts were a source of strength for us during this time, We are also indebted to our friends, family, colleagues and well-wishers from all over the world who stood by us during our need.”A longtime friend and colleague of Nargeolet told French media that when contact was lost Sunday, he quickly feared the worst.“Unfortunately, I thought straight away of an implosion,” diver and retired underwater filmographer Christian Pétron said Friday to broadcaster France-Info. At the depths in which the submersible was operating, the pressure is intense and unforgiving, he noted.“Obviously, the slightest problem with the hull and its implosion is immediate,” Pétron said.Video below: Debris field identified as pieces of missing of Titanic subDirector James Cameron, who has made multiple dives to the wreckage of the Titanic, told the BBC that he knew an “extreme catastrophic event” had happened as soon as he heard the submersible had lost navigation and communications at the same time.“For me, there was no doubt," Cameron said. "There was no search. When they finally got an ROV (remotely operated vehicle) down there that could make the depth, they found it within hours. Probably within minutes.”He said briefings about 96 hours of oxygen supply and banging noises were a “prolonged and nightmarish charade” that gave the crew members’ families false hope.At least 46 people successfully traveled on OceanGate’s submersible to the Titanic wreck site in 2021 and 2022, according to letters the company filed with a U.S. District Court in Norfolk, Virginia, that oversees matters involving the Titanic shipwreck. But questions about the submersible's safety were raised by both by a former company employee and former passengers.David Lochridge, OceanGate’s former director of marine operations, argued in 2018 that the method the company devised for ensuring the soundness of the hull — relying on acoustic monitoring that could detect cracks and pops as the hull strained under pressure — was inadequate and could “subject passengers to potential extreme danger in an experimental submersible.”OceanGate disagreed. Lochridge “is not an engineer and was not hired or asked to perform engineering services on the Titan,” it said, and it noted he was fired after refusing to accept assurances from the company's lead engineer that the acoustic monitoring and testing protocol was, in fact, better suited to detect flaws than a method Lochridge proposed.One of the company’s first customers likened a dive he made to the site two years ago to a suicide mission.“Imagine a metal tube a few meters long with a sheet of metal for a floor. You can’t stand. You can’t kneel. Everyone is sitting close to or on top of each other,” said Arthur Loibl, a retired businessman and adventurer from Germany. “You can’t be claustrophobic.”___Associated Press writers Jon Gambrell in Dubai, United Arab Emirates; Ben Finley in Norfolk, Virginia; Holly Ramer in Concord, New Hampshire; Lolita C. Baldor in Washington; Frank Jordans in Berlin; Danica Kirka in London; Gene Johnson in Seattle; Munir Ahmed in Islamabad; and John Leicester in Paris contributed to this report.

The company whose submersible vanished in the North Atlantic on a tourist dive to the wreck of the Titanic was repeatedly warned that there might be catastrophic safety problems posed by the way it was developed, documents show.Related video above: Underwater noises detected in search for missing submersibleWith five people aboard a vessel that if still functioning would have a dwindling amount of oxygen, an expanding international fleet of ships and airplanes is searching for the Titan, operated by OceanGate Expeditions. The undersea exploration company based in Everett, Washington, has been making yearly voyages to the Titanic since 2021.In the first piece of good news since the search began, a Canadian aircraft detected underwater noises, though the vessel has not been found, the U.S. Coast Guard reported early Wednesday.David Lochridge, OceanGate's director of marine operations, wrote an engineering report in 2018 that said the craft under development needed more testing and that passengers might be endangered when it reached "extreme depths," according to a lawsuit filed that year in U.S. District Court in Seattle.OceanGate sued Lochridge that year, accusing him of breaching a non-disclosure agreement, and he filed a counterclaim alleging that he was wrongfully fired for raising questions about testing and safety. The case settled on undisclosed terms several months after it was filed.Lochridge's concerns primarily focused on the company's decision to rely on sensitive acoustic monitoring — cracking or popping sounds made by the hull under pressure — to detect flaws, rather than a scan of the hull. Lochridge said the company told him no equipment existed that could perform such a test on the 5-inch-thick carbon-fiber hull."This was problematic because this type of acoustic analysis would only show when a component is about to fail — often milliseconds before an implosion — and would not detect any existing flaws prior to putting pressure onto the hull," Lochridge's counterclaim said.Further, the craft was designed to reach depths of 13,123 feet, where the Titanic rested. But, according to Lochridge, the passenger viewport was only certified for depths of up to 4,265 feet, and OceanGate would not pay for the manufacturer to build a viewport certified for 4,000 meters.OceanGate's choices would "subject passengers to potential extreme danger in an experimental submersible," the counterclaim said.However, the company said in its complaint that Lochridge "is not an engineer and was not hired or asked to perform engineering services on the Titan." He was fired after refusing to accept assurances from OceanGate's lead engineer that the acoustic monitoring and testing protocol was, in fact, better suited to detect any flaws than a scan would be, the complaint said.OceanGate Chief Executive Stockton Rush defended the approach in a speech to a conference in Seattle last year hosted by the tech news site GeekWire. He described how he had taken a prototype down to 4,000 meters: "It made a lot of noise," he said.So he brought the vessel back up, and on a second dive, it made the same troubling noises, even though it should have been dramatically quieter. The company scrapped that hull, which had been constructed by a marine manufacturer, and built another one with an aerospace supplier, Rush said.In an emailed statement, a spokesman for the company said the missing sub was completed in 2020-21, so it would not be the same as the vessel referenced in the lawsuit.OceanGate also received another warning in 2018, this one from the Marine Technology Society, which describes itself as a professional group of ocean engineers, technologists, policy-makers and educators.In a letter to Rush, the society said it was critical that the company submit its prototype to tests overseen by an expert third party before launching in order to safeguard passengers.Rush had refused to do so.Rush was piloting the vessel that is now missing.The letter, reported by the New York Times, said society members were worried that "the current experimental approach adopted by Oceangate could result in negative outcomes (from minor to catastrophic) that would have serious consequences for everyone in the industry."In a 2019 interview with Smithsonian magazine, Rush complained that the industry's approach was stifling innovation."There hasn't been an injury in the commercial sub industry in over 35 years," he said. "It's obscenely safe because they have all these regulations. But it also hasn't innovated or grown — because they have all these regulations."

A submersible carrying five people to see the remains of the Titanic at the bottom of the North Atlantic Ocean is still missing despite a massive search operation – but banging sounds were reportedly heard in the area Tuesday as time runs out.Search teams heard the sounds in 30-minute intervals Tuesday, according to an internal government memo update on the search. Banging was still heard four hours later, after additional sonar devices were deployed.A subsequent update sent Tuesday night suggested more sounds were heard, though it was not described as “banging.” Still, it indicates “continued hope of survivors,” the update said.CNN has reached out to OceanGate, the US Coast Guard in Boston and Canadian authorities for comment. Rolling Stone was first to report the news Tuesday night.The Titan submersible had been on its way to the famous wreckage, off the coast of St John’s, Newfoundland, in Canada, when it lost contact with its support ship, leaving the people on board with only enough oxygen for a few days.Here's what we know so far:How did they go missing?The submersible was part of an eight-day journey conducted by OceanGate Expeditions. The trip is based out of Newfoundland, with participants first traveling 400 nautical miles to the wreck site, which is about 900 miles off the coast of Cape Cod, Massachusetts. The submersible began its two-hour descent to the wreck on Sunday morning. It lost contact with the Polar Prince, the support ship that transported the vessel to the site, 1 hour and 45 minutes into its descent, officials said. Search operations began later that day.It’s still not clear what happened to the submersible, why it lost contact, and how close to the Titanic it was when it went missing.Who's on board?The five people on board include one pilot and four “mission specialists,” said Rear Adm. John Mauger, commander of the U.S. Coast Guard’s First District.OceanGate CEO and founder Stockton Rush is among those onboard, according to a source with knowledge of the mission plan.A British businessman based in the United Arab Emirates, Hamish Harding, is also onboard, according to a social media post by the company he owns, Action Aviation.“The sub had a successful launch and Hamish is currently diving,” the company said in an Instagram post on Sunday.Harding was one of the first people to travel the Challenger Deep in the Pacific Ocean – the deepest known point on Earth.On Saturday he wrote of the Titanic mission: “I am proud to finally announce that I joined OceanGate Expeditions for their RMS TITANIC Mission as a mission specialist on the sub going down to the Titanic.”Harding had posted on social media Saturday saying that diver Paul-Henri Nargeolet was scheduled to be on Sunday’s dive with him. Nargeolet has led several expeditions to the Titanic and supervised the recovery of many artifacts from the wreck, according to the E/M Group, where Nargeolet was director of underwater research.CNN has attempted to reach out independently to Nargeolet with no success.A Pakistani businessman, Shahzada Dawood, and his son Sulaiman Dawood, were also on board, according to a statement released by the family on Tuesday. Contact has been lost and there is limited information available, it said.Shahzada Dawood is a trustee of the SETI Institute, a research organization in California, according to its website. He is also vice chairman of Dawood Hercules Corporation, part of the Dawood Group, a conglomerate of various businesses owned by the family.Authorities have not publicly identified the passengers on board, and said Monday they are still notifying their families.The OceanGate website says its expeditions, which cost upwards of $250,000, typically involve one pilot, a “content expert” and three paying passengers.How much time do they have?Coast Guard officials estimated on Monday afternoon the submersible had “somewhere between 70 to the full 96 hours” of oxygen – potentially giving rescuers until Friday to locate and retrieve the vessel. On Tuesday, U.S. Coast Guard officials said at a 1 p.m. ET news conference that the submersible has about 40 hours of oxygen left.But there are a number of challenges, including the remote location, local weather conditions, the state of the submersible – and the extraordinary depth of the ocean in the area they went missing.The deepest ever underwater rescue was that of Roger Chapman and Roger Mallinson, who were rescued from the Pisces III submersible at depths of 1,575 feet in 1973. They were trapped for 76 hours before finally being hauled to the surface.The Titanic wreckage is much deeper, sitting nearly 13,000 feet below sea level. It’s not clear how deep the submersible is. Some experts have pointed out it might be near the surface, since submersibles typically are able to shed weight for additional buoyancy. But even if they reach the surface, the door is bolted from the outside – meaning they still risk running out of oxygen unless they are located and freed by rescuers.What is the submersible? What’s it like inside?A submersible is different from a submarine in a few key ways. It has limited power reserves, so it needs a support ship on the surface to launch and recover it. It can’t stay underwater for as long; the Titan typically spends 10 to 11 hours during each dive to the Titanic wreck, compared to submarines that can stay underwater for months.The Titan is made of carbon fiber and titanium, weighing 23,000 pounds, with safety features to monitor the structure integrity of the vessel, according to OceanGate.It’s also small and sparse on the inside, with about as much space as a minivan, according to CBS correspondent David Pogue, who took a trip on the Titan down to the Titanic wreck last year. There is only one toilet, and no seats; passengers sit cross legged on the floor. There are no windows except the porthole through which passengers view the Titanic.With no GPS underwater, the submersible is only guided by text messages from the surface ship. On Pogue’s trip, communications broke down during a dive and the submersible was lost for over two hours, he said.The pilot steers the sub using a video game controller – but if that fails, a hard-wired system can control the propellers, according to Aaron Newman, who took the dive on the Titan in 2021 and is now an OceanGate investor. Thrusters are powered by an external electrical system, while an internal system powers communications and a heater, he said. What search operations are underway? How might it be rescued?Multiple agencies from both the US and Canada are involved in the search, looking both on the surface and underwater. More than 10,000 square miles have been searched as of Tuesday.Boats, aircraft and radar equipment are scanning above water in case the submersible had surfaced. Sonar buoys and sonar equipment on ships are also being used to detect sounds below water.The US Coast Guard, US Navy, US Air Force, Canadian Coast Guard, and Canadian military are all coordinating the search and potential rescue operations. France has also sent a research ship, equipped with an underwater robot, to join the search.Deep sea-mapping company Magellan, most famously known for its one-of-a-kind deep sea imagery of the Titanic, is also working to get its equipment to the site.But finding the submersible is just the first step; rescuing it could be a whole other challenge.Depending where and at what depth the submersible is found, there could be limited options for rescue vessels.For instance, the US Navy’s nuclear-powered submarines usually operate at 800 feet or less – meaning they can’t dive down to the ocean floor, where water pressure on the submarine hull could make it implode.During the 1973 rescue, authorities used other submersibles and a remotely operated, Navy-developed recovery vessel to attach lines to the Pisces III – which were then used to pull it back to the surface.It’s not clear whether these methods could work for the Titan, given the uncertainty around its location.Have there been safety concerns before?The incident has prompted discussion around the safety of deep-sea tourism, with some pointing out that OceanGate has come under criticism before.Two former OceanGate employees separately brought up similar safety concerns about the thickness of the Titan’s hull when they were employed by the company years ago.A statement from a research lab also appears to show conflicting information about the engineering and testing that went into the development of the vessel.OceanGate’s legal representative boasted the Titan’s “unparalleled” safety features in a 2021 court filing, saying it had been built with the University of Washington’s Applied Physics Laboratory – but the university said the lab had never dealt with the design, engineering or testing of the Titan.Industry leaders also expressed concerns five years ago about the company’s “experimental approach” to the Titan submersible and its trip to the Titanic, the New York Times reported Tuesday.The Manned Underwater Vehicles committee of the Marine Technology Society said it penned a letter to Rush, the missing CEO, in 2018. The group warned of potential “negative outcomes (from minor to catastrophic) that would have serious consequences for everyone in the industry,” said the letter obtained by the Times.OceanGate has not responded to a request for comment on the letter, or on the two former employees’ claims.

Rescue crews searching for a submersible with five people aboard are keeping a nervous eye on the craft's dwindling oxygen supply.

The U.S. Coast Guard launched a search and rescue operation Monday to locate a submersible that went missing during an expedition taking tourists to the wreckage of the Titanic, CNN partner CTV News reported.The group conducting the trip, Oceangate Expeditions, said it is "exploring and mobilizing all options to bring the crew back safely.""Our entire focus is on the crewmembers in the submersible 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 reestablish contact with the submersible," the group said. "We are working toward the safe return of the crewmembers."CNN has reached out to the Boston Coastguard and authorities in Newfoundland, Canada.The Titanic infamously hit an iceberg on its maiden voyage and sank in the North Atlantic Ocean in April 1912, killing over 1,500 people. The wreckage of the Titanic, discovered in 1985, sits in two parts at the bottom of the ocean nearly 13,000 feet below the surface southeast of Newfoundland.More recently, costly private tours have been offered to tourists, allowing people to see the wreck up close. An archived version of OceanGate's website, accessible via the Internet Archive's Wayback Machine, lays out what passengers can expect on the $250,000 trip."Follow in Jacques Cousteau’s footsteps and become an underwater explorer – beginning with a dive to the wreck of the RMS Titanic. This is your chance to step outside of everyday life and discover something truly extraordinary," the website said. "Become one of the few to see the Titanic with your own eyes."The eight-day expedition is based out of St. John's, Newfoundland, Canada, with a maximum of six people. The trip begins with a 400-nautical-mile journey to the wreck site.Related video above: 3D scan of Titanic reveals never-before-seen detailsThere, up to five people, including a pilot, a "content expert" and three paying passengers, board the submersible named "Titan" and descend to the bottom of the ocean."Once the submersible is launched you will begin to see alien-like lifeforms whizz by the viewport as you sink deeper and deeper into the ocean. The descent takes approximately two hours but it feels like the blink of an eye," the website said. This is a developing story. Check back for updates.