NEW : CNN : eight instances of Russian aircraft in European airspace in late Wednesday . NATO said that in a 24-hour period ending late Wednesday , there were more than 19 instances of Russian aircraft in European airspace . Groups of Russian aircraft detected over areas of the Atlantic Ocean , North , Black seas . NATO : `` Unusual level of air activity over European airspace '' NATO official tells NATO the recent flights could be possible prelude to Russian air exercises .
NEW : CNN : eight instances of Russian aircraft in European airspace in late Wednesday . Groups of Russian aircraft detected over areas of the Atlantic Ocean , North , Black seas . NATO : `` Unusual level of air activity over European airspace '' NATO official tells NATO the recent flights could be possible prelude to Russian air exercises .