Search underway for missing submarine en route to Titanic wreckage.

A submarine carrying one pilot and four passengers, including British billionaire Hamish Harding, went missing off the coast of southeastern Canada while taking tourists to explore the wreckage of the Titanic. U.S. and Canadian ships and planes have been deployed to search for the missing submarine, called the Titan, which has the capacity to be submerged for 96 hours. The private company that operates the submarine, OceanGate Expeditions, said it was "mobilizing all options" to rescue those on board. The expeditions, which cost $250,000 per person, start in St. John's, Newfoundland, before heading out approximately 400 miles (640 km) into the Atlantic to the wreckage site.