An undated photo shows tourist submersible belongs to OceanGate descents at a sea. Search and rescue operations continue by US Coast Guard in Boston after a tourist submarine bound for the Titanics wreckage site went missing off the southeastern coast of Canada. RACE AGAINST TIME - Missing sub nears critical deadline when oxygen was projected to run out. Continue reading … AMERICAN DETAINED - WSJ reporter Evan Gershkovich's appeal denied by Russian court. 'BASELESS DISTORTIONS' - Adam Schiff censured by House for'false' allegations on Trump-Russia collusion.

The U.S. Coast Guard said Tuesday afternoon that there around 40-41 hours of "breathable air" left on the OceanGate Titan submersible that disappeared en route to the Titanic wreckage in the North Atlantic. Deep-sea vehicle industry insiders say the combination of the enormous depth, the lack of communication and the rapidly dwindling window of opportunity make rescue of the five people aboard the OceanGate highly unlikely. The OceanGate was bringing its passengers to see the wreckage of the Titanic, about 12,500 below sea level, when it went missing on Sunday. The OceanGate has about 40 hours of oxygen remaining, the Coast Guard reported Tuesday afternoon, assuming the vehicle did not suffer an instant catastrophic explosion, as some experts have said they fear. "The math is not great," one career expert in autonomous underwater vehicles, more commonly known as drones, told Fox News Digital.