The incursion on Wednesday was followed by a second incident on Thursday involving two Russian long-range bombers, which flew into Canada's air defense identification zone (ADIZ) and were intercepted by two Canadian F-18 jets, officers said.
In both cases the Russian aircraft flew out of the area without incident.
The Russian warplanes "never entered US sovereign air space" or Canadian air space, said Major Jamie Humphries, a spokesman for the North American Aerospace Defense Command.