OceanGate's sub incident is resurfacing years-old safety concerns about the company

OceanGate uses its Titan vessel to take tourists deep below sea level to visit the Titanic shipwreck. It disappeared in the North Atlantic during one such trip on Sunday. (AP)

Experts from within and outside OceanGate raised concerns about the safety of its Titan submersible as far back as 2018, years before it went missing during a deep-sea dive to the Titanic shipwreck site.

Several of those complaints have resurfaced this week, as the frantic search for the vessel — and its five passengers — continues.