Caitlin Wilson
Live editor

After a week of testimony at the inquiry into last year's Titan disaster, there is still more testimony to come on Monday.

The Friday session included testimony from an expert in the submersible industry and a researcher who quit OceanGate due to safety concerns.

Antonella Willby, a former OceanGate contractor who worked for the Titan's communication and navigation team described multiple safety breakdowns, including when an unexplained "bang as loud as an explosion" was heard from the sub and company executives failed to investigate the cause.

She was told she did not have "an explorer's mindset" and opted to leave the mission, ending her contract early.

Her testimony came after an appearance by Patrick Lahey, an executive from Triton, a company which manufacturers and sells submersibles.

Lahey said that aside from the Titan, the industry had a "50-year track record of perfect safety" and said he believed that submersibles will become ubiquitous in a generation.

On Monday, the panel will hear from Guillermo Sohnlein, who co-founded OceanGate in 2009 with the company's late CEO Stockton Rush.

It will also hear from Phil Brooks, OceanGate's former director of engineering, and Roy Thomas from the American Bureau of Shipping.

In the meantime, we are concluding our live coverage of this story for now.

You can catch up on all the updates from this week here: Key takeaways from first week of Titan sub hearings

Our writers for this page have been Max Matza, Madeline Halpert and Rebecca Morelle. It has been edited by Marita Moloney and me.

Thank you for joining us.

Rebecca Morelle
Science editor

OceanGate took paying passengers down to see Titanic – a place on the Titan sub could cost up to $250,000 (£187,700).

They were given a particular title – “mission specialists” – and invited to get involved with the sub operations beyond the dive, becoming part of the expedition’s crew.

This could be seen as part of OceanGate’s marketing approach, offering customers more of an experience rather than just a tourist trip to the deep.

But some of the experts I’ve spoken to say they think the company had a different motive.

They believe that describing passengers as part of the crew rather than as paying customers was a way to get around complying with safety and liability issues linked to passenger transport.

Rebecca Morelle
Science editor

We've seen that the US Coast Guard, external has released a transcript of a key meeting that took place on 18 January, 2018 in Everett, Washington.

It’s a conversation between David Lochridge - OceanGate’s former director of marine operations - and OceanGate CEO Stockton Rush, plus three other staff members from the company.

Lochridge, the whistleblower who told the hearing earlier this week that he recorded this conversation, is there to discuss a report he has compiled about his safety concerns.

The names of the people who are speaking on the transcript, external are redacted, but much of the discussion appears to be a heated exchange between two people. The BBC has contacted the US Coast Guard to confirm the names of the two people.

The transcript shows one person raise many problems with the sub’s design - including the poor quality of the material it was made of. Lochridge told the US Coast Guard about his concerns over these issues at the hearing on Tuesday.

In the transcript, the speaker says: “I am addressing what I view as safety concerns, concerns I have mentioned verbally… which have been dismissed by everybody.”

In response, another one of the meeting’s attendees says: “Everything I've done on this project is people telling me it won't work - you can't do that.”

They continue: “I have no desire to die. I've got a nice granddaughter. I am going to be around. I understand this kind of risk, and I'm going into it with eyes open and I think this is one of the safest things I will ever do."

Later they say: “I can come up with 50 reasons why we have to call it off and we fail as a company. I'm not dying. No one is dying under my watch period.”

David Lochridge was fired after the meeting.

Rebecca Morelle
Science editor

The public hearings have heard from several former OceanGate employees - and their repeated warnings about the sub’s safety.

On Tuesday, David Lochridge - the company’s former director of marine operations, told the US Coast guard that he’d had serious problems with the sub’s design.

He said he’d warned OceanGate about the poor quality of the material the sub was made of - carbon fibre - and told the hearing that he thought it was “inevitable” that something would go wrong.

He was fired by the company in 2018, so took his concerns to the US Occupational Safety and Health Administration. But he said they were slow and failed to act - and after increasing pressure from OceanGate’s lawyers, he dropped the case and signed a non disclosure agreement.

At the end of his evidence, he said that if the authorities had properly investigated OceanGate then the tragedy might have been averted.

Earlier we heard from Patrick Lahey, the co-founder of Triton submersibles, who told the Coast Guard panel about the importance of certifying sub vessels.

"Certification matters because it's about building something that's robust, durable, reliable" and something people can "dive in with confidence", Lahey said.

"Any machine that's going to be carrying human beings into the deep sea has to meet the high bar of certification" by a third-party group, he said, adding:

"I don't believe that we should be operating experimental vehicles in the deep sea."

That wraps up today's hearing, during which we heard the testimonies of four people about the Titan sub implosion last year.

We've still got some more posts to bring you, so stay with us.

Antonella Willby, a field roboticist who previously worked as a contractor with OceanGate, goes on to say that she felt compelled to "reach out to the board of directors" after hearing about the report of a loud bang on Titan a year before the fatal implosion.

Another OceanGate colleague told her she should be concerned about being sued if she made her complaints publicly known, so she opted to keep silent, she tells the hearing.

Asked to describe the "safety culture" at OceanGate, she replies: "I saw what I would classify as safety theatre."

She says there were "lots of people walking around with expensive safety gear". But the company was not willing to have conversations about their safety protocols, Wilby says.

Once, when she raised basic questions about safety while diving, she says she was told: "Don't worry it'll be fun. You'll have fun."

She says she decided not to go on further dives with OceanGate after feeling like her concerns were not heard.

Willby, who says that she quit OceanGate over safety concerns, said that the company did not seem prepared during their missions to the wreck of the Titanic.

"I'm certainly no expert in composites. It also appeared that there were no other experts in carbon composites aboard," she says about her July 2022 trip.

Titan's hull was made of carbon fiber, a composite material, unlike with most submersibles which are made of harder metals such as titanium.

Willby says that the company accused her of having a bad attitude after she expressed concerns that OceanGate was not taking safety seriously.

She said she "didn't have an explorer mindset" in response to her concerns about what a passenger said was a "bang as loud as an explosion" that occurred when the Titan was resurfacing in July 2022.

"We're cowboys and we're innovators," she says chief executive Stockton Rush told her.

An OceanGate employee later asked her if she wanted to continue on the mission or to go home. She opted to be sent home, and left the next day, Wilby tells the hearing.

Image source, US Coast Guard inquiry

Antonella Wilby, a contractor who worked as a field roboticist for OceanGate, is next to testify.

She is asked to describe an incident in July 2022, when the Titan sub made a loud bang sound after resurfacing.

"I wasn't aware until the next day that anything had gone wrong," she says.

A debrief was delayed until the next morning, she says.

"One customer stated on ascent that as they were getting close to the surface they heard a bang as loud as an explosion."

OceanGate chief executive Stockton Rush tried to quickly brush past the comment, she says. He claimed that "deep sea vehicles make lots of noise", she adds.

"It seemed like the customers concerns were not taken seriously during that debrief," Wilby says.

We've just finished hearing testimony Patrick Lahey, the chief executive of Triton submersibles - a leading manufacturer of deep sea crafts.

Lahey repeatedly claimed that subs are safer than any other form of transportation. But he said he was only referring to subs that had undergone classification assessments from an independent third body, unlike OceanGate's Titan.

During questioning, he delivered an impassioned defence of the submersible industry, saying that he had warned OceanGate that its sub was "not ready" to carry humans underwater.

He also revealed that he once had a off-hand chance to tour the Titan, or possibly a prototype that preceded it, during testing in the Bahamas.

While on holiday, a person spotted him wearing the T-shirt for his company and asked if would be interested in seeing the sub.

He called the sub not "particularly well thought-out" and said the operators seemed "amateurish in its execution".

He condemned OceanGate CEO Stockton Rush for avoiding certifying the company's sub, saying that Rush considered the optional regulatory process to be "an impediment to innovation".

He also called upon government bodies to mandate that all subs be classified in the future.

Lahey has just wrapped up his testimony, giving an impassioned speech about the kinds of opportunities deep-sea exploration can provide - if the right safety measures are taken.

He says submersibles are "the most magical machines" that foster an interest and love of sea exploration.

"They transport human beings to what I consider to be the most beautiful part of our world, what I consider to be the deep sea," he says.

Image source, Pelagic Research Services/U.S. Coast Guard

A member of the panel is asking Lahey how to prevent another tragedy like the Titan implosion in the future.

Lahey insists on certification - saying a review from an independent party should be a requirement.

"Human exploration of the deep sea requires certification," he repeats, a refrain he has gone back to several times during this testimony.

Lahey says that regulators must “insist” on classification requirements for all submersibles. Only unclassed subs, like Titan, are at risk of failure, he says.

“I can’t think of any other mode of transportation that can boast a 50-year track record of perfect safety," he says, referring to fully certified submersibles.

An investigator with the National Transportation Safety Board (NTSB) asks Lahey if he believes submersibles will be "ubiquitous" within the next generation.

"I certainly hope so," the witness replies with a bit of a chuckle.

The investigator asks if changes will need to be made to make them safer as they become more common.

"The rules are constantly evolving, as most things are," he replies.

Lahey goes on to agree that as the technologies change, the way that subs are tested will have to change too.

Lahey is asked if he is familiar with the last time passengers on a submersible were killed during a dive.

He recalls the Johnson Sea Link, a sub which belonged to the Harbor Branch Oceanographic Institute became ensnared in a net off the coast of Florida in 1973.

Two people in the diver lockout compartment died from a combination of carbon dioxide poisoning and hypothermia, Lahey says.

Lahey says he noticed a number of issues with the Titan when he saw it.

He says the vessel did not seem "particular well thought out".

"It just looked amateur-ish in its execution," he says, adding they could have made improvements in the time after he saw it.

Lahey says he left the visit relieved because he thought the submersible would never see the light of day.

We're back from a break, and Lahey is telling the panel that there is no reason why experimental submersibles, like Titan, couldn't have been certified.

He said it might have taken more time and resources, but the certification process mattered greatly for safety.

Lahey says OceanGate CEO Stockton Rush viewed the certification as "an impediment to innovation".

Rebecca Morelle
Science editor

Patrick Lahey spoke to the BBC before the public hearing - and was highly critical of the sub.

“The OceanGate contraption was an aberration. It was not the way people in our community typically go about building and operating as sub,” he told me.

By chance, he saw the Titan sub being tested in the Bahamas in 2019 - he happened upon the OceanGate team while he was on holiday there.

“It was clear, as I looked at the vehicle, that it was very poor in its execution,” he said.

“There were a lot of things that, you know, I pointed out that I felt were unsafe.

“The ideas that I saw, many of which were really half baked, just led me to believe there's just no way that anybody's going to dive in that thing.”

The hearing has now gone to a short break, and will reconvene shortly with more questions for Lahey.

Stick with us.

Lahey calls it a "myth" that submersibles are unsafe.

He says that OceanGate was wrong to send an experimental craft into the deep sea, and notes his own "unblemished" 50 year record of "playing around" with submersibles.

"I think its an important thing to bear in mind that the certification process works," he says.

"Our track record on safety proves it. And as far as I'm concerned, we need to insist on continued human exploration of the deep sea in certified and accredited machines. Not experimental ones."