Algeria's national airline, Air Algerie, says it has lost contact with one of its planes flying from Burkina Faso to Algiers across the Sahara.
Contact was lost about 50 minutes after take-off from Ouagadougou, the airline said.
The passenger airliner was last seen at 0155 GMT, it added. It should have landed at 0410.
Flight AH 5017 had 110 passengers and six crew on board, Spanish airline Swiftair, which owns the plane, said.
"In keeping with procedures, Air Algerie has launched its emergency plan," Air Algerie officials, quoted by APS news agency, said.
The plane is operated by Air Algerie and chartered from Swiftair.
In a statement (in Spanish), Swiftair said that the aircraft was an MD83 and that they were unable to establish contact with the plane.