(PERTH, Australia) -- Search crews have stopped seeking pinger signals in the search for missing Malaysia Airlines Flight 370, and an underwater vessel will now be deployed in the southern Indian Ocean, a process that officials are describing as painstaking and slow. Angus Houston, retired Australian Air Chief Marshal, who is head of the joint agency coordinating the search for the missing jetliner, discussed the updates at a Monday press conference.
Houston said the Bluefin-21 will be deployed, creating a sonar map of the area to chart any debris on the sea floor. So far, crews have detected four signals consistent with the pings of an airplane's black box. But the black box pingers only have battery life for about a month -- and given the plane’s March 8 disappearance, officials believe too much time has passed for any new signals.
"We haven't had a single detection in six days, and I guess it's time to go under water," Houston said.
Officials are hoping to find the black boxes in order to understand what happened to the jetliner, which disappeared with 239 people on board.
Houston warned that the switch to the submarine "will be a slow and painstaking process."
The Bluefin-21 will take a total of 24 hours to conduct each mission. Two hours will be needed for the sub to get to the bottom of the ocean, 16 hours for it to execute its search, two more hours for it to return to the surface, and another four hours to download and analyze the data it collected.
Search crews will continue scouring the area for visual debris, with 12 planes and 15 ships involved in Monday’s efforts.
Copyright 2014 ABC News Radio