Two missiles were reportedly fired at a Russian plane with at least 159 passengers on board as it was flying over Syrian territory on Monday.
Russian officials, though admitting the plane might have been endangered, are not yet talking of a targeted attack.
Russia's federal air traffic agency Rosaviatsia has issued a warning to all Russian airlines to avoid routes over conflict zones.
The plane that was allegedly targeted belonged to Nordwind Airlines -- a Russian charter air carrier -- and was identified as an Airbus A320.
On April 29 the aircraft was en route to the city of Kazan, in Russia's republic of Tatarstan, from Egypt's resort city of Sharm el-Sheikh. So far, there are no grounds to claim that the aircraft became a target of a missile attack, military experts say.