A prolonged undersea search for the missing Malaysia Airlines Flight 370 could cost nearly a quarter of a billion U.S. dollars if private companies are used , Australia 's top transport official said Thursday . Martin Dolan emphasized that the $ 234 million price tag is a `` ballpark rough estimate '' of an extended search and salvage mission that includes an underwater vehicle . The Bluefin-21 is back at work Friday morning on a fifth trip into the southern Indian Ocean . Authorities said the vessel has scanned a total of 110 square kilometers ( 42.5 square miles ) without making any `` contacts of interest . '' Searchers seem to be preparing for the possibility that an underwater drone scan of the ocean may not yield debris from the plane immediately . Malaysia 's acting transport minister , Hishammuddin Hussein , said that authorities are looking at deploying more unmanned underwater probes . Officials might consider searching along a large portion of sea highlighted by a partial digital `` handshake '' between the jetliner and an Inmarsat PLC satellite , Dolan said . That arc of sea is over 370 miles long and 30 miles wide . Underwater search . Officials did n't indicate whether Bluefin 's fourth mission was a lengthy one . The Bluefin was forced to abort its mission twice this week ; the first time after it exceeded its original depth limit and the second time over a technical issue . After the latter was resolved , officials dipped it into the ocean again . Phoenix International Holdings , which owns and operates the equipment under a contract for the U.S. Navy , called the third dive `` very productive , '' saying that the underwater drone spent nearly 13 hours at the sea bottom . But after four dives , `` there has been no debris or aircraft wreckage discovered , '' the company said . The underwater vessel takes two hours to get near the ocean floor and another two hours to return to the surface . It aims to map the ocean floor for 16 hours to retrieve data , which then take four hours to analyze . The vessel searches maximum depths of 4,500 meters ( 14,764 feet ) . The U.S. Navy has determined the seafloor in the search area reaches a maximum depth of 4,600 meters ( 15,092 feet ) . Bluefin operators said they can reprogram it to operate at 5,000 meters ( 16,404 feet ) , giving it more leeway . New setbacks . Officials believe a recent ping heard in the search area has the right frequency to belong to the flight data recorder 's emergency beacon . The quality of the `` ping '' led authorities to focus the underwater search in the area . And as the underwater focus continues , officials faced other setbacks . A preliminary analysis of an oil sample collected in the ocean shows that it is not aircraft engine oil or hydraulic fluid , Australia 's Joint Agency Coordination Centre said Thursday . Malaysia Airlines Flight 370 vanished on March 8 with 239 people aboard after taking off from Kuala Lumpur , Malaysia , bound for Beijing . With no debris found so far and no possible pings from the plane 's `` black boxes '' detected in a week , officials shifted the focus of the search underwater .
Malaysian official raises the possibility of more underwater search vehicles . The Australian Transport Safety Bureau (ATSB) said it was investigating whether a new type of submersible vehicle could be used to help locate MH370. Bluefin-21 has covered 110 square kilometers in four trips . A preliminary analysis of an oil sample shows that it is not aircraft engine oil .