Search teams looking for a submersible near the wreck of the Titanic called in specialist deep-sea recovery equipment as they clung to hopes the five-man crew is alive and can be saved during the final remaining hours of available air.

A fleet of search ships have amassed in the North Atlantic about 900 miles (1,450 kilometers) east of Cape Cod, Massachusetts, since the vessel went missing Sunday on a dive to survey the Titanic. The U.S. Coast Guard said Wednesday the Navy is sending a lifting system to the area that can recover large and heavy sunken objects such as aircraft or small boats from deep water.

Time is crucial for the missing crew, if they are still alive and their vessel remains intact. The Titan, which started with about 96 hours of air in case of an emergency, is theoretically down to its final reserves. The crew is also believed to have limited food and water.