Angus Houston, chief of the Joint Agency Coordination Centre, has today announced that the next phase in the search will begin as soon as possible with the deployment of a Bluefin-21 autonomous underwater vehicle. A recent set of four signals that may have come from the airplanes black boxes has helped this effort, and today Air Chief Marshal Houston has noted the discovery of an oil slick in the vicinity as well. The batteries on the MH370 black boxes are only rated to last for 30 days, so continuing to listen out for their pings would now be more hopeful than helpful. While he describes the current information as the most promising lead that weve had through the entire search, he also cautions that it may be very difficult to find something and you dont know how good any lead is until you get your eyes on the wreckage. Rated for a depth of 4.5 kilometers, the Bluefin drone appears to be the best available method for extending the search in the absence of any further signals from the black boxes.