THE TOP FIVE THEORIES

BOMB

A loss of cabin pressure caused by a bomb could explain why no one sent a distress signal or regained control, and why wreckage was found in more than one area. A bomb on a timer – perhaps smuggled on at an African stop earlier that day – might be more likely than a suicide bomber, who would want to detonate over Paris or Cairo for maximum carnage.

HIJACKING

The plane’s swerves may indicate a life-or-death fight in the cockpit. The argument against this is that no one managed to send a mayday, which suggests a hijacker would have had to break into the cockpit extremely quickly – or had inside help. They would also have had to contend with three air marshalls on the flight.

ROGUE PILOT

The lack of a distress signal could be explained if a pilot crashed on purpose. In the Germanwings Airbus

A320 crash in March 2015, co-pilot Andreas Lubitz locked the captain out of the cockpit and flew into a mountain, killing all 150 people on board. EgyptAir says terrorism is more likely than a mechanical fault, and experts say there is almost no mechanical fault that would explain the pilots being unable to trigger a distress signal, even if they were wrestling for control of the plane. The same argument can be made against the theory of pilot error. A less likely possibility is a missile strike, similar to the one that downed Malaysian Airlines flight MH1 over Ukraine in July 2014, killing 298 people. But the EgyptAir flight was too high to be reached by a shoulderlaunched missile and there is no obvious land mass nearby for a fixed missile launcher capable of targeting a plane at high altitude.