A British billionaire is one of five people aboard a submersible tourist vessel that went missing during a voyage to the Titanic shipwreck.Hamish Harding, chairman of private plane firm Action Aviation, is understood to be aboard the five-person OceanGate Expeditions vessel, which was reported overdue on Sunday evening about 435 miles south of St John's, Newfoundland.A major search and rescue operation, being led by the US Coast Guard and involving military aircraft, is under way.

A British billionaire is one of five people aboard a submersible tourist vessel that went missing during a voyage to the Titanic shipwreck.Hamish Harding, chairman of private plane firm Action Aviation, is understood to be aboard the five-person OceanGate Expeditions vessel, which was reported overdue on Sunday evening about 435 miles south of St John's, Newfoundland.A major search and rescue operation, being led by the US Coast Guard and involving military aircraft, is under way.