San Francisco, June 21 : A whistleblower had raised serious safety concerns about OceanGate's tourist submarine called Titan that went missing with five people during an expedition to the Titanic's wreckage in the North Atlantic. He was later fired after presenting a "scathing quality control report on the vessel". David Lochridge, director of marine operations at OceanGate, was terminated after raising concerns about its first-of-a-kind carbon fiber hull and other systems before its maiden voyage, according to a filing in a 2018 lawsuit. He was fired after presenting the report on the vessel to OceanGate's senior management, including founder and CEO Stockton Rush, who is on board the missing vessel, reports TechCrunch. The report detailed "numerous issues that posed serious safety concerns," according to the filing. These included "visible flaws" in the carbon fibre supplied to OceanGate raised the risk of small flaws expanding into larger tears during "pressure cycling." These are the huge pressure changes that the submersible would experience as it made its way and from the deep ocean floor. Lochridge wrote that a previously tested scale model of the hull had "prevalent flaws." Carbon fiber composites can be stronger and lighter than steel, making a submersible naturally buoyant. But they can also be prone to sudden failure under stress. Lochridge's recommendation was that non-destructive testing of the Titan's hull was necessary to ensure a "solid and safe product," according to the filing. Lochridge was reportedly told that such testing was impossible. He was worried that the system would not reveal flaws until the vessel was descending, and then might only provide "milliseconds" of warning before a catastrophic implosion. A few months after Lochridge's termination, the company had published a blog post stating reasons for not having Titan certified by the American Bureau of Shipping. "The vast majority of marine (and aviation) accidents are a result of operator error, not mechanical failure. As a result, simply focusing on classing the vessel does not address the operational risks. Maintaining high-level operational safety requires constant, committed effort and a focused corporate culture -- two things that OceanGate takes very seriously and that are not assessed during classification," the blog post read. Meanwhile, the US Coast Guard on Wednesday confirmed that a Canadian P-3 aircraft "detected underwater noises in the search area" for the missing tourist submarine with five people on board. The submarine was lost about an hour and 45 minutes into its dive to the Titanic's wreckage in the Atlantic on June 18, according to the Coast Guard. The five passengers on board are Hamish Harding, a 58-year-old British adventurer; UK businessman Shahzada Dawood (48) and his son Suleman (19); Paul-Henry Nargeolet (77), a former French Navy diver, and Rush (61), the OceanGate CEO. /IANS