New video footage released by the United States Airforce Europe shows two Russian jets being intercepted.
Tensions over Ukraine keep prominent Western heads of state away from Russian Victory Day parade.
NATO's rapid reaction force is now expected to respond in just 48 hours.
"Do not provoke the Russian bear," said Russia's ambassador to Denmark after joking about Sweden's paranoia
An official said the flights—which have risen 50 percent over the last year—posed a risk to commercial air traffic.
Last month, NATO said it had conducted more than 100 intercepts of Russian aircraft this year, about three times as many as in 2013.