Air France has suggested that the plane could have been stuck by lighting which is seen as a common hazard. A lightening bolt could have been reason enough to cause the crash but the four-year-old flight may have faced other problems such as violent turbulence, the authorities said.
Other theories that have come up include pilot error, mechanical defects or even the remote possibility of terrorism.
However, no hypothesis is favored now said the French PM Francois Fillon.
"Our only certainty is that there was no distress call sent by the plane, but regular automatic alerts sent over three minutes indicated the failure of all systems," he added on Tuesday, Jun 2.