Australian Prime Minister Tony Abbott, right, chats with his Malaysian counterpart Najib Razak at Perth International Airport as Razak prepares to depart Australia after his visit during the search of the missing Malaysia Airlines flight MH370, in Perth, Australia, Thursday, April 3, 2014. Najib arrived at the Australian air force base serving as a hub for the search for Flight 370, as the coordinator of the multinational search effort warned that the hunt for the jetliner was one of the most complicated searches in history. Najib met with Abbott and received a briefing by Angus Houston, the head of a joint agency coordinating the search. (AP Photo/Paul Kane, Pool)