Australian Prime Minister Tony Abbott said Monday that search operations for missing Malaysia Airlines flight MH370 have entered a new stage which will involve a more comprehensive approach to scour the ocean floor using side-scan sonar, capable of covering 700 square kilometres at a time.

The new phase will still involve the Bluefin-21 autonomous vehicle, Ret. Australian Air Chief Marshal Angus Houston said Monday but side-scan sonar can pick up imagery in real-time while the Bluefin-21 device requires you to download data every 20 hours.

Since the aircraft disappeared on March 8 with 239 people aboard, Australia has coordinated the search for 42 of the 53 days as of Tuesday. “In this period, more than 4.5 million square kilometres of ocean has been searched,” Abbott said. In addition, there have been 334 Australian search flights—an average of eight per day equal to over 3,000 flight hours.

Prime Minister Abbott said the new search will also involve private contractors during the estimated eight month search going forward, with a cost of $60 million barring any setbacks. Houston, who is leading the search in Perth, said any delays involving weather or equipment malfunctions will setback the search and inflate the cost. There were six Australian citizens and one resident on board MH370.

The United States has spent $11.4 million USD to search for MH370, Pentagon spokesman Army Col. Steve Warren said Thursday. This figure includes the $4,200 per flight hour flight cost of the P-8 Poseidon aircraft currently deployed near Australia, Warren said. Three American citizens were on board MH370.

Japan, China, New Zealand, the United Kingdom and Malaysia have contributed assets to the search since the jetliner vanished. “Enormous efforts have been made. Enormous efforts will continue to be made,” Abbott said while reinforcing that Malaysia Airlines has requested his country’s involvement in subsequent MH370 investigations should they lead elsewhere.

“This is probably the most difficult search in human history,” the prime minister said.