The submersible that was reported missing while on a tour of the underwater wreckage of the Titanic is an unorthodox vessel with a relatively unproven history, according to company press materials and experts familiar with underwater vehicles.

News of the vessel's disappearance prompted a flurry of interest in the company OceanGate Expeditions and its deep-sea submersible called the Titan.

The company's founder and CEO, Stockton Rush, who is one of the five people aboard the missing vessel, manned the Titan's first "validation dive" to 4,000 meters in 2018, according to the company. The company then began offering tourists the opportunity to dive to the depths of the Titanic in the following years, selling tickets for the 2023 journey for $250,000.

Here's what we know about how the submersible operates.

-ABC News' Peter Charalambous

A source familiar confirmed to ABC News that there were reports of "banging" that were picked up by sonar in the search area on Tuesday morning, but nothing has yet been found.

The U.S. Coast Guard had said early Wednesday that an aircraft with sonar capability "detected underwater noises in the search area," but remotely operated vehicles were unable to find the origin of the sound.

-ABC News' Luke Barr

Magellan, an international exploration company that digitally mapped the Titanic wreckage last year, said Wednesday that it is "ready to support" the search for the missing submersible and is "fully mobilized to help."

The U.K.-based company told ABC News that it was contacted by the submersible’s operator, OceanGate Expeditions, early Monday and "immediately offered our knowledge of the specific site and also our expertise operating at depth considerably in advance of what is required for this incident."

"We have been working full-time with U.K. and U.S. agencies to secure the necessary air support to move our specialist equipment and support crew," Magellan said in a statement.

When asked for comment about media reports that U.S. authorities have failed to give Magellan the necessary permits to participate in the search, the company told ABC News it "does not not wish to comment on any specific media report."

-ABC News' Emma Ogao

The U.S. Coast Guard announced via Twitter early Wednesday that a Canadian aircraft with sonar capabilities had "detected underwater noises in the search area."

Remotely operated vehicle operations (ROV) were then relocated "in an attempt to explore the origin of the noises," according to the Coast Guard.

"Those ROV searches have yielded negative results but continue," the Coast Guard tweeted.

OceanGate co-founder Guillermo Söhnlein is coming to the defense of late CEO Stockton Rush, one of those killed in the implosion of Titan, after criticism from director James Cameron, and others, who said the sub's carbon-fiber hull was dangerous.

"In this kind of community, there are completely different opinions and views about how to do things, how to design submersibles, how to engineer them, build them, how to operate in the dives," Söhnlein told the U.K.'s Times Radio on Friday. "But one thing that’s true of me and the other experts, is none of us were involved in the design, engineering, building, testing or even diving of the subs. So it’s impossible for anyone to really speculate from the outside."

Söhnlein co-founded OceanGate in 2009 with Rush and led several dives in the early days of the company. He left OceanGate in 2013, when Rush took over as CEO, but maintained a friendship and spoke to Rush just weeks before the doomed expedition, he said on Facebook.

Cameron, who not only directed the Oscar-winning film "Titanic" but is a prolific ocean explorer, criticized the use of a carbon-fiber hull in the construction of Titan, saying it was only a matter of time before it cracked under the pressure from repeated dives. Rush, in the past, defended its use, saying it had a better strength-to-buoyancy ratio than titanium.

"I was involved in the early phases of the overall development program during our predecessor subs to Titan, and I know from firsthand experience that we were extremely committed to safety and risk mitigation was a key part of the company culture," Söhnlein told Times Radio Friday.