In race against clock, expanding fleet of ships searches for submersible lost near Titanic wreck
prativad 
In a race against the clock on the high seas, an expanding international armada of ships and airplanes searched Tuesday for a submersible that vanished in the North Atlantic while taking five people down to the wreck of the Titanic.
US Coast Guard officials said the search covered 10,000 square miles (26,000 square kilometers) but turned up no sign of the lost sub known as the Titan. Although rescuers planned to continue looking, time was running out because the vessel would have less than two days of oxygen left if it is still intact and functioning.
"This is a very complex search, and the unified team is working around the clock,” Cpt. Jamie Frederick of the First Coast Guard District in Boston told a news conference.
Frederick said the crew would have no more than about 41 hours of oxygen remaining as of midday Tuesday. That means its air supply could run out Thursday morning.
