A U.S. military spokesman says Russian military flights over European airspace are raising tensions and pose a potential danger to security and to civilian aircraft.
Rear Admiral John Kirby told reporters in Washington that the flights of Russian warplanes "pose the potential risk of escalation."
There was another round of Russian flights on October 31, with NATO monitoring Russian planes over the Baltics, the North Sea and the Atlantic Ocean.
"The aircraft involved fighter jets, long-range bombers and tanker aircraft," Kirby said.
NATO earlier this week said Russian military aircraft engaged in large-scale flight operations in European airspace on October 28 and 29 and alliance planes were sent up to intercept and identify them.
NATO says there have been more than 100 intercepts of Russian aircraft in 2014 to date, about three times the number in 2013.