BANGING sounds have been heard underwater in the search for the missing Titan submersible, sparking new hope that crew members could be signaling for help.
Searchers said they heard banging in 30-minute intervals while looking for the vessel, which disappeared on Sunday during an underwater trip to see the Titanic wreckage.
A Canadian aircraft detected the sounds in the area where the divers disappeared, though the US Coast Guard did not elaborate on what rescuers believe the noises could be.
It offers a glimmer of hope, however, for the missing sub as teams race against time to rescue those on board before their oxygen supply runs out on Thursday.
Underwater drones have now been redeployed in a bid to locate where the thuds came from, but have so far "yielded negative results".
The US Coast Guard said: "Canadian P-3 aircraft detected underwater noises in the search area.
"As a result, ROV operations were relocated in an attempt to explore the origin of the noises. Those ROV searches have yielded negative results but continue.
"Additionally, the data from the P-3 aircraft has been shared with our U.S. Navy experts for further analysis which will be considered in future search plans."
US Navy officials have also scrambled a so-called Flyaway Deep Ocean Salave System to the scene, which is able to lift small vessels.
The banging sounds were detected every 30 minutes, according to emails sent to the Department of Homeland Security seen by .
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Another aircraft located a white rectangular object in the water but a ship sent to investigate changed course to look into the banging, reported.
A pal of trapped British billionaire Hamish Harding said the regular banging is exactly the tactic his friend would employ if stranded in the depths of the Atlantic.
Chris Brown, an explorer and friend of Mr Harding, told BBC Breakfast the reported banging sounds has "got them written all over it".
He added it was "just the sort of thing I would have expected Hamish to come up with".
Chris - who signed up for a Titanic trip at the same time as his pal in 2016 - pulled out of the OceanGate programme over safety fears about the quality of equipment and material used.
But he has also saluted his space tourist and explorer pal’s coolness in a crisis, declaring he would do everything possible to survive.
Chris said: "If you made a continuous noise, that's not going to get picked up, but doing it every 30 minutes, that suggests humans.
"I'm sure they're all conserving oxygen and energy, because it's cold and dark down there."
Passengers paid $250,000 (£195,000) per head for an eight-day excursion starting and ending at St John’s, Newfoundland.
After traveling by boat, the team started to descend 12,5000ft the ocean surface for a view of the Titanic's remains.
However, the sub, named Titan, lost contact with its mother ship just two hours into the underwater dive on Sunday.
Search crews from multiple countries are frantically trying to find the vessel, which was believed to have 40 hours of oxygen left as of Tuesday afternoon.
The passengers stuck on the sub alongside Mr Harding are OceanGate CEO Stockton Rush, British-based tycoon Shahzada Dawood and his 19-year-old son Suleman, and French diving expert Paul-Henry Nargeolet.
The president of the Explorers Club, an international association that advances exploration efforts and technology, said that "signs of life" at the site were "cause for hope."
Hamish is a founding member of the board of trustees of the group, which has been involved in many of the world's most prestigious discoveries.
"We have much greater confidence that there is cause for hope based on data from the field - we understand that likely signs of life have been detected at the site," the group wrote.
The club said that it is ready to provide 6,000-meter certified remote-operated vehicles to help in the search for the missing passengers.
They added: "We continue to work on approval for the Magellan ROVs to be allowed to deploy to the site as we believe they can provide invaluable assistance.
"Our hearts are with family and friends of fellow Explorers Club members Hamish Harding and Paul-Henri Nargeolet, and the rest of the submersible crew as we await hopefully good news."
David Mearns, a deep sea hunter and friend of Harding, was also encouraged by the reports of banging sounds and has hope despite a believed one percent chance of survival.
"They've got sonobuoys out there... there may be some other hydrophones at the mothership," Mearns told
"They're at least trying to operate or encourage the rescue efforts to continue."
OceanGate boasts state-of-the-art technology that can advance human exploration to unprecedented depths.
This heavily complicates rescue efforts as first responders have only been able to safely dive 2,000 feet below the surface.
The US Navy shared plans on Tuesday to send a deep-water lifting system to help with search efforts.
During a press conference on Tuesday afternoon, First District Response Coordinator Capt. Jamie Frederick said officials have already scoured a 7,600 square mile area - which is roughly the size of Connecticut.
Canadian forces and a number of private vessels are also aiding the search.
Even if they're able to locate the missing vessel before its oxygen supplies run out on Thursday morning, Frederick conceded there was no guarantee that rescuers will be able to bring the sub to the surface.
OceanGate, one of few companies offering trips to see the Titanic ruins, confirmed a major search mission has been launched to "bring the crew back safely."
The deepest successful underwater rescue in history was in 1973 when British engineers Roger Mallinson and Roger Chapman were saved after their submersible became trapped on the seabed at 1,575ft.
This operation would be 11,000ft deeper.
SAFETY FEARS
It comes as ex-passengers have also told tales of radio failures and flickering lights while onboard the Titan.
Mike Reiss, who works on the classic US TV animated show The Simpsons, made the trip last year on the sub Titan and said communication failures were common.
He said: “I have taken three different dives with this company, one at the Titanic and two others and you almost always lost communication — and you are at the mercy of weather.”
Renata Rojas, a banker who visited the wreckage last July, described what happened when sonar failed during her trip.
She said: “You have to find a way to communicate and navigate in the bottom of the ocean.
“Sometimes you don’t have communications, you have maybe just one system instead of all three.
“Some of the lights may flicker... The battery might be low and you need to go to the surface.”
France's oceanographic institute is currently sending its vessel Atalante to the scene - carrying their underwater robot Victor 6000.
The ship should arrive at the Titan's last known location at 6pm on Wednesday.
The robot has the ability to search at 20,000ft.
NO CONTACT
Titan is understood to have lost contact with the Polar Prince just one hour and 45 minutes into the expedition.
Every 15 minutes, Titan also sends "pings" to the Polar Prince.
The final of these pings is understood to have been sent at around 11.30am local time on Sunday, directly above the Titanic.
After that, no contact was had with the vessel at all - but Canada's Coast Guard wasn't alerted until after 9pm.
The family of Dawood and his son Suleman - who recently graduated from International School Cobham - have asked for people to "pray for their safety."
They said: "We are very grateful for the concern being shown by our colleagues and friends and would like to request everyone to pray for their safety."
Mr Darwood is vice chairman of Dawood Hercules Corporation, part of the Dawood Group, which has been a family business for more than a century, according to Seti Institute's website.
He and his family live in a gated home in Surrey, and a neighbor told The Sun that the house was currently being renovated and that they had been away for some time.
He described them as a humble couple who threw garden parties for their neighbours having been at the private home for the past eight or nine years.
Another passenger, 58-year-old aviator and businessman Mr Harding, is known as one of the leaders of the record-breaking mission to orbit the Earth via both poles in 2019.
His stepson confirmed that he was one of the crew on board the sub.
Mr Harding posted on Facebook about poor weather conditions before the trip began.
He said: "Due to the worst winter in Newfoundland in 40 years, this mission is likely to be the first and only manned mission to the Titanic in 2023.
"A weather window has just opened up and we are going to attempt a dive tomorrow."
French submersible pilot Paul-Henry Nargeolet, 73, is also feared to be on board.
Mr Nargeolet is the Director of the Underwater Research Program at Premier Exhibitions, RMS Titanic, Inc.
The diving expert previously spoke frankly of the extreme dangers of deep-sea exploration in an interview.
He said: “If you are 11m or 11km down, if something bad happens, the result is the same.
“When you’re in very deep water, you’re dead before you realize that something is happening, so it’s just not a problem.”
The group has been accompanied by Stockton Rush, the Chief Executive Officer and Founder of OceanGate Inc - the company carrying out the expedition.
Last year he told : "Titan is the only five-person sub capable of going to the Titanic depth, which is half the depth of the ocean.
"There are no switches and things to bump into, we have one button to turn it on.
"Everything else is done with touch screens and computers, and so you really become part of the vehicle and everybody gets to know everyone pretty well."
DOOMED VOYAGE
The Titanic sank on its maiden voyage to New York on April 14, 1912, after hitting an iceberg.
More than 1,500 of the 2,200 passengers and crew onboard were killed, and many died within minutes of being thrown into the -2C waters.
The decaying wreck of the 822ft liner was first discovered in 1985 but due to its depth and strong currents even the best underwater cameras have only offered a small snapshot into its colossal remains.
Its bow and the stern that broke apart during the sinking lie more than 2,600ft apart and are surrounded by an unending field of exposed debris.
But last month, the ship's haunting wreck was revealed as never before in stunningly detailed 3D scans on the ocean floor.
Scientists hope the high-resolution digital images - the clearest view ever of the world's most famous shipwreck - could shed new light on the disaster.
The British luxury passenger liner took under three years to construct, costing around $1.6million - equating to about $185million today.
Thousands of workers were involved in the project, with some 14,000 men employed during the peak of construction.
The frame was fully formed in just over a year, with the shell plating finished shortly afterward.
The steamship was released from its dry dock in 1911 and work on the interior began.
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Just eight days before its maiden voyage, it was declared seaworthy.