The time frame for the investigation was initially a year, but the inquiry has taken longer.

The Coast Guard said in July that the hearing would delve into “all aspects of the loss of the Titan,” including both mechanical considerations as well as compliance with regulations and crew member qualifications.

The Titan had been making voyages to the Titanic wreckage site going back to 2021.

The Titan became the subject of scrutiny in the undersea exploration community in part because of its unconventional design and its creator’s decision to forgo standard independent checks.

The implosion killed Rush and veteran Titanic explorer Paul-Henri Nargeolet; two members of a prominent Pakistani family, Shahzada Dawood and his 19-year-old son Suleman Dawood; and British adventurer Hamish Harding.

The Titan made its final dive on June 18, 2023, losing contact with its support vessel about two hours later.

When it was reported overdue, rescuers rushed ships, planes and other equipment to an area about 435 miles (700 kilometers) south of St. John’s, Newfoundland.

The search for the submersible attracted worldwide attention, as it became increasingly unlikely that anyone could have survived the implosion.

Wreckage of the Titan was subsequently found on the ocean floor about 300 meters (330 yards) off the bow of the Titanic, Coast Guard officials said.

Scheduled to appear later in the hearing are OceanGate co-founder Guillermo Sohnlein; former operations director, David Lochridge; and former scientific director, Steven Ross, according to a list compiled by the Coast Guard.

Numerous guard officials, scientists, and government and industry officials are also expected to testify.

The US Coast Guard subpoenaed witnesses who were not government employees.

OceanGate has no full-time employees at this time but will be represented by an attorney during the hearing, the company said in a statement.

The Coast Guard does not comment on the reasons for not calling specific individuals to a particular hearing during ongoing investigations, said Melissa Leake, a spokesperson for the Coast Guard.

She added that it’s common for a Marine Board of Investigation to “hold multiple hearing sessions or conduct additional witness depositions for complex cases.”

Among those killed was Stockton Rush, co-founder of OceanGate, the Washington state company that owned the Titan.

The company suspended operations after the implosion.

Witnesses scheduled to testify on Monday include OceanGate’s former engineering director, Tony Nissen; the company’s former finance director, Bonnie Carl; and former contractor Tym Catterson.

Some key OceanGate representatives are not scheduled to testify.

They include Rush’s widow, Wendy Rush, who was the company’s communications director.

The ongoing Marine Board of Investigation is the highest level of marine casualty investigation conducted by the Coast Guard.

When the hearing concludes, recommendations will be submitted to the Coast Guard’s commandant.

“There are no words to ease the loss endured by the families impacted by this tragic incident,” said Jason Neubauer of the Coast Guard Office of Investigations, who led the hearing.

“But we hope that this hearing will help shed light on the cause of the tragedy and prevent anything like this from happening again.”

Coast Guard officials also gave an overview of the history of the Titan, during which they stated that the hull of the craft was never subject to third-party checks.

Officials also said the sub was left exposed to weather and elements while in storage for seven months in 2022 and 2023.

The Titan imploded in June 2023, sparking a worldwide debate about the future of private undersea exploration.

The aim of the hearing in Charleston County, South Carolina, is to “uncover the facts surrounding the incident and develop recommendations to prevent similar tragedies in the future,” the Coast Guard said in a statement earlier this month.