An Air Algerie flight from Burkina Faso to Algiers disappeared from radar early Thursday, the official Algerian news agency said.
Air navigation services lost track of the plane after 0155 GMT, or 50 minutes after takeoff, the agency said. That means that Flight AH5017 had been missing for hours before the news was made public.
"In keeping with procedures, Air Algerie has launched its emergency plan," the agency quoted the airline as saying.
The flight path of the plane from Ouagadougou, the capital of the west African nation of Burkina Faso, to Algiers was not immediately clear.
Ougadougou is in a nearly straight line south of Algiers, passing over Mali where unrest continues in the north.
However, a senior French official said it was unlikely that fighters in Mali had weaponry that could shoot down a plane. The official, who spoke on condition of anonymity because she was not authorized to speak for attribution, said the fights have shoulder-fired weapons which could not hit an aircraft at cruising altitude.
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