Experts raised safety concerns about missing Titanic submersible in 2018

FILE PHOTO: The Titan submersible, operated by OceanGate Expeditions to explore the wreckage of the sunken SS Titanic off the coast of Newfoundland, dives in an undated photograph. OceanGate Expeditions/Handout via REUTERS

(Reuters) -Experts raised safety concerns in 2018 about the submersible vessel that has been missing since Sunday, when it descended with tourists on a deep ocean journey to view the wreckage of the Titanic.

The pilot and four passengers are aboard and the available oxygen on the vehicle has been forecast to run out by Thursday morning.