A friend said he warned Stockton Rush about possible defects on the Titan in 2019 after hearing 'cracking' noises

• A friend of Stockton Rush told CNN that he heard "cracking" sounds after a Titan trip in 2019.
• Karl Stanley emailed Rush to say that the noises "sounded like a flaw/defect," CNN reported.

A submersible expert and friend of Stockton Rush, the CEO of OceanGate, said he tried to warn him that the Titan sub was flawed years ago.

Karl Stanley told NewsNation that he heard "cracking" sounds when he went on the sub in April 2019.

Stanley said Rush told him to be prepared for the cracking sounds he heard on the Titan's first dive, which Rush said the vessel's carbon-fiber material produced.

Stanley said he heard the "sound of the cracking getting louder" after they took the sub deeper on the Titan's second dive in the Bahamas.

The next day, he emailed Rush about possible defects. "What we heard, in my opinion… sounded like a flaw/defect in one area being acted on by the tremendous pressures and being crushed/damaged," Stanley told Rush in emails seen by CNN.

"From the intensity of the sounds, the fact that they never totally stopped at depth, and the fact that there were sounds at about 300 feet that indicated a relaxing of stored energy /would indicate that there is an area of the hull that is breaking down/ getting spongy," he wrote.

Stanley asked Rush if he was considering taking passengers on it to see the Titanic before he knew what was causing the sounds, CNN reported, but that he didn't get a response.

Stanley said he first met Rush about a decade ago and that he "liked him as a friend."

A former OceanGate employee also warned the company about inadequate "quality control and safety" protocols in a lawsuit filed in August 2018.

David Lochridge, the former director of marine operations, said that Rush asked him to carry out a quality inspection of the sub, and found there was a lack of testing carried out on the hull.

He made the claims in a countersuit against OceanGate after it accused him of breach of contract. The case was settled out of court in November 2018.

Lochridge said that he'd raised his concerns with OceanGate's management and that he was fired after the meeting.

OceanGate did not immediately respond to a request for comment from Insider sent outside regular business hours.