The submersible is operated by OceanGate Expeditions, a company that offers tours of shipwrecks and underwater canyons. It said on its website that an expedition was “currently underway.”

“Our entire focus is on the crew members in the submersible and their families,” a statement said. “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.”

Hamish Harding, the chairman of the aviation company Action Aviation, is among those aboard the missing submersible, according to Mark Butler, the company’s managing director. Mr. Harding wrote on his Facebook page on Saturday that a dive had been planned for Sunday: “A weather window has just opened up,” he wrote.

Here’s what to know about the search operation:

• The chief executive of OceanGate, founded in 2009, has compared its project to the booming space tourism industry. Its customers pay $250,000 to travel to the wreckage on the seabed, more than two miles below the ocean’s surface. Read about OceanGate here.

• John Lockwood, a longtime OceanGate board member, said the company’s submersibles have a viewing port and external cameras. “But it’s not like going down in a submarine at a very shallow depth, where there are multiple viewing ports,” he said.

• OceanGate chartered a vessel, the MV Polar Prince, to serve as the ship on the surface near the dive site. The company’s website outlines an eight-day itinerary for the trip out of St. John’s, Newfoundland, Canada. The site says customers do not require any previous diving experience, but that there are “a few physical requirements like being able to board small boats in active seas.”

• The Titanic sank in the early hours of April 15, 1912, on its maiden voyage from England to New York after hitting an iceberg, killing more than 1,500 people. The wreckage was found in 1985, broken into two main sections, about 400 miles off Newfoundland, in eastern Canada. Read The Times’s coverage of the sinking.

Made of titanium and carbon fiber, it weighs about 21,000 pounds and is listed as measuring 22 feet by 9.2 feet by 8.3 feet, with 96 hours of “life support” for five people.

The Titan, one of three types of crewed submersibles operated by OceanGate, is equipped with a platform similar to the dry dock of a ship that launches and recovers the vessel, the website said.

“The platform is used to launch and recover manned submersibles by flooding its flotation tanks with water for a controlled descent to a depths of 9.1 meters (30 feet) to avoid any surface turbulence,” according to the website.

“Once submerged, the platform uses a patented motion-dampening flotation system to remain coupled to the surface yet still provide a stable underwater platform from which our manned submersibles lift off of and return to after each dive,” the site continues. “At the conclusion of each dive, the sub lands on the submerged platform and the entire system is brought to the surface in approximately two minutes by filling the ballast tanks with air.”

OceanGate calls the Titan the only crewed submersible in the world that can take five people as deep as 4,000 meters — or more than 13,100 feet — enabling it to reach almost 50 percent of the world’s oceans. Unlike other submersibles, the Titan, the website said, employs a system that can analyze how pressure changes affect the vessel as it dives deeper, providing “early warning detection for the pilot with enough time to arrest the descent and safely return to surface.”

The Titan began deep-sea ventures related to the Titanic in 2021. According to the tech news site GeekWire, the vessel was “rebuilt” after OceanGate determined through testing that the vessel could not withstand the pressure of a 4,000-meter dive.

Mauger said that one of the aircraft being used in the search could detect underwater noises.“But it is a large area of water, and it’s complicated by local weather conditions as well,” he said.

First there was the team that took undersea robots to depths of more than 12,000 feet, verifying that the broken hulk it found at the bottom was in fact the Titanic. Then came many others, including James Cameron, the director who reinvigorated interest in the ship with his 1997 film, “Titanic.”

The ship had long garnered intense interest among researchers and treasure hunters captivated by the tragic history of the wreck: the horror of the accident, the supposed hubris of the ship’s builders, the enormous wealth of many and the poverty of others on the luxury liner juxtaposed with the cold facts of the iceberg and the sea.

But Mr. Cameron’s hit imbued the wreck with a new story of romance and tragedy, renewing interest far beyond those with an interest in famous accidents at sea.

By the early 2000s, scientists were warning that visitors were a threat to the wreck, saying that gaping holes had opened up in the decks, walls had crumpled, and that rusticles — icicle-shaped structures of rust — were spreading all over the ship.

Tourists were paying up to $36,000 per dive by submersible. Salvage crews hunted for artifacts to bring back up, over the objections of preservationists who said the wreck should be honored as the graveyard for more than 1,500 people. Wreckage from a submersible accident was found on one of the Titanic’s decks. Researchers said the site was littered with beer and soda bottles and the remains of salvage efforts, including weights, chains and cargo nets.

Mr. Cameron, who has repeatedly visited the wreck, was among those calling for care around the site. In 2003, he took 3D cameras there for his 2003 documentary, “Ghosts of the Abyss.”

OceanGate Expeditions, the private company operating the submersible that went missing on Monday, was founded in 2009. By the time it began offering tours to paying customers, researchers said that the Titanic had little scientific value compared to other sites.

But cultural interest in the Titanic remains extraordinarily high: OceanGate charges $250,000 for a submersible tour of the wreck, and the disaster continues to command a fascination online, sometimes at the expense of facts.

“No public entity is going to fund going back to the Titanic,” Mr. Rush said. “There are other sites that are newer and probably of greater scientific value.”

OceanGate takes paying tourists in submersibles to underwater canyons and shipwrecks, including the Titanic. Last year, it shared a one-minute clip of video obtained during one of its trips to the wreck site, which was discovered in 1985, less than 400 miles off Newfoundland.

The dives last about eight hours, including the estimated 2.5 hours each way it takes to descend and ascend. Scientists and historians provide context on the trip and some conduct research at the site, which has become a reef that is home to many organisms. The team also documents the wreckage with high-definition cameras to monitor its decay and capture it in detail.

Mr. Rush said that the high quality of the footage allowed researchers to get an even closer look at the site without having to go underwater. He compared the OceanGate trips to space tourism, saying the commercial voyages were the first step to expanding the use of the submersibles for industrial activities, such as inspecting and maintaining underwater oil rigs.

“For those who think it’s expensive, it’s a fraction of the cost of going to space and it’s very expensive for us to get these ships and go out there,” Mr. Rush said. “And the folks who don’t like anybody making money sort of miss the fact that that’s the only way anything gets done in this world is if there is profit or military need.”

Then P.A.S. Franklin, Vice President and General Manager of the International Mercantile Marine, conceded that probably only those passengers who were picked up by the Cunarder Carpathia had been saved. Advices received early this morning tended to increase the number of survivers by 200.

The admission followed a day in which the White Star Line officials had been optimistic in the extreme. At no time was the admission made that every one aboard the huge steamer was not safe. The ship itself, it was confidently asserted, was unsinkable, and inquirers were informed that she would reach port, under her own steam probably, but surely with the help of the Allan liner Virginian, which was reported to be towing her.

As the day passed, however, with no new authentic reports from the Titanic or any of the ships were known to have responded to her wireless call for help, it became apparent that authentic news of the disaster probably could come only from the Titanic’s sister ship, the Olympic.

The wireless range of the Olympic is 500 miles. That of the Carpathia, the Parisian, and the Virginian is much less, and as they neared the position of the Titanic they drew further and further out of shore range. From the Titanic’s position at the time of the disaster it is doubtful if any of the ships except the Olympic could establish communication with shore.