American and Canadian fighter jets scrambled this week to investigate why Russian planes were flying in international airspace west of Alaska — on the same days Ukraine's president addressed lawmakers in Canada and Washington, D.C. While the encounter was professional and without confrontation, the number and type of Russian planes intercepted was unique, a senior defense official told NBC News on Friday. Two American fighter jets intercepted six Russian planes, including two fighter jets, over the Air Defense Identification Zone (ADIZ) on Wednesday, while Canadian fighter jets intercepted two Russian Bear long-range bombers on Thursday over the ADIZ, the official said.

Russia sends planes into ADIZ space — extending about 200 miles from the Alaskan coastline — about 10 times a year. But it usually only dispatches a couple of them and almost never sends fighter jets in addition to bombers and refuelers, according to the official, adding that the U.S. hasn't seen these types of planes in ADIZ space since Cold War days. Planes are also rarely sent to both the U.S. and Canadian ADIZ within such a short period. Ukrainian President Petro Poroshenko met with Canadian lawmakers on Wednesday and addressed Congress in Washington on Thursday.

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— Courtney Kube and Elisha Fieldstadt