The sister of the billionaire businessman and his son who are aboard the Titan submersible that disappeared on a dive to the Titanic wreck says her family is fully focused on their safe return.

Businessman Shahzada Dawood and 19-year-old Suleman Dawood are still missing along with CEO and founder of OceanGate Expeditions Stockton Rush, British billionaire explorer Hamish Harding and renowned French diver Paul-Henri Nargeolet.

Mr Dawood’s sister, Sabrina Dawood, told Sky News that the Dawood family is solely focused on the rescue of her brother and nephew and hope for their safe return.

“We are deeply grateful for the efforts of news agencies during this difficult time; your constant coverage of the missing Titan submersible is undoubtedly playing a large role in the world’s ability to access relevant updates on the matter,” she told the British news channel.

“At this time, the Dawood family’s sole focus is the rescue of our beloved Shahzada and Suleman Dawood and we are unable to address any questions or comments at the moment.

Graeme Massie reports:

The US Coast Guard offered more insight into the mysterious “banging” noises that crew searching for the missing surmisable heard.

Captain Jamie Frederick of the US Coast Guard said that airplanes that detected the noises on Tuesday also heard them on Wednesday but the results were inconclusive.

Mr Frederick said upon hearing the sounds, ROVs (remote operated vehicles) were re-located to investigate where they were coming from. However, they did not find the missing submersible nor found out where the sounds were coming from.

Experts in the US are analysing the noises to better understand where or what they could have come from.

Carl Hartsfield, director and senior program manager, of the Woods Hole Oceanographic Institution said that it’s possible an underwater animal could have made the noises.

Rescue ships with crucial deep ocean ROVs (remote operated vehicles) will only arrive on site after the missing Titan submersible crew members run out of oxygen, the US Coast Guard said in a press conference on Wednesday (21 June).

Captain Jamie Frederick, the response coordinator for the First Coast Guard District said that five rescue vessels will arrive in the next 24-48 hours, after the estimated time when the Titan’s oxygen reserves will have been exhausted.

Bevan Hurley reports:

Captain Jamie Frederick said that the US Coast Guard was working closely with the French and British governments who have offered assets and experts to aid in the search for the submersible.

The French research vessel L’Atalante changed course to head to the remote area of the North Atlantic, at the director of French President Emmanuel Macron.

The vessel is equipped with an exploration robot that can dive to the depths of the Titanic shipwreck.

Captain Jamie Frederick said in addition to the “banging” sounds that one asset detected on Tuesday and Wednesday, one aircraft saw something floating in the water –both were investigated with no results.

Mr Frederick said when the aircraft spotted something they went back to look at it but determined it was “not correlated with the case.”

The result of the “banging” noises heard by the Canadian P-3 was inconclusive but the results had been shared with the US for further analysis, Mr Frederick said.

In a press conference on Wednesday (21 June), Captain Jamie Frederick, response coordinator from the First District of the US Coast Guard, said the US had five surface assets searching for the missing submersible with five more coming in the coming days.

Two ROVs (remotely operated vehicles) are currently searching for the OceanGate Expeditions sub, with “several more” en route.

In addition, two P-3 flights and two C-130s flights were surveying the area on Wednesday.

“We will continue to work as hard and quickly as possible to locate them,” Captain Frederick said.

Rescuers frantically searching for the missing Titan submersible may take hope from a successful mission which saw a crew saved after spending 84 hours trapped underwater.

The ongoing race to find the group has led to comparisons with a successful mission to save two submariners trapped 150 miles off the coast of Ireland back in 1973.

Roger Mallinson and Roger Chapman endured almost three-and-a-half days trapped in Pisces III while it lay about 1,600ft (500m) below sea level.

The pair - then aged 28 and 35 respectively - eventually reached the surface with just 12 minutes of oxygen left.

Speaking shortly after it emerged that the crew aboard the missing OceanGate Expeditions vessel have less than 24 hours of oxygen left, Mr Mallison said: “It’s very cold and it’s very dark and it’s really frightening because you don’t know what the outcome is going to be.

Oliver Pritchard-Jones reports: