Russian airline companies have cancelled dozens of flights and four airports are planning brief closures as Russia hosts massive military exercises in the south and the annexed Crimean peninsula.

Russia on Monday launched six days of military drills involving 12,500 troops, fighter jets, anti-aircraft missiles and other weaponry. The defense ministry said in a statement it dispatched more than 30 military aircraft on Wednesday to check the readiness of Russia's air defense in the south.

Russia's flagship airline Aeroflot says it was cancelling six flights scheduled for Thursday from Moscow to the south because of the exercises. Other airlines canceled about 20 more flights.

Four airports in the south, including one in the Crimean capital of Simferopol, said they would close briefly Thursday morning because of the drills.