A French ship joined the international effort to hunt for the black boxes and other wreckage of EgyptAir Flight 804 Monday, searching for clues to what brought the plane down, as Greek and Egyptian authorities diverged on what happened to the plane during the crucial final minutes before it crashed into the Mediterranean, killing all 66 people on board.

Five days after the air disaster, questions remain over what happened to the doomed jet before it disappeared off radar at around 2.45 a.m. local time Thursday.

Egyptian authorities said they believe terrorism is a more likely explanation than equipment failure, and some aviation experts have said the erratic flight reported by the Greek defense minister suggests a bomb blast or a struggle in the cockpit. But so far no hard evidence has emerged.

A 2013 report by the Egyptian ministry of civil aviation records that the same Airbus 320 made an emergency landing in Cairo that year, shortly after taking off on its way to Istanbul, when one of the engines "overheated." Aviation experts have said that overheating is uncommon yet is highly unlikely to cause a crash.... Read More: ABC News