Russian military aircraft are posing a threat to civilian planes by turning off communications devices and failing to file flight plans, the U.S. ambassador to NATO said on Monday.
Russia has stepped up flights near NATO's borders, the alliance says, coinciding with increased East-West tension over Russia's role in the Ukraine crisis. NATO aircraft have scrambled more than 400 times this year to intercept Russian aircraft, up 50 percent from the 2013 total.
U.S. Ambassador Douglas Lute said there had been "multiple incidents" where Russian military aircraft had not filed flight plans or spoken to civilian air traffic controllers, and had turned off transponders that send information about their aircraft.