The North American Aerospace Defense Command detected a Russian aircraft flying near Alaska on Monday, amid several planned military exercises in the area.

The aircraft was in international airspace, NORAD said, and did not enter Alaskan or Canadian airspace. It did enter the Alaska Air Defense Identification Zone. The zone, called ADIZ, "begins where sovereign airspace ends and is a defined stretch of international airspace," NORAD said in a news release.

NORAD did not elaborate on which military training exercises were ongoing, but did say they were "large-scale" and taking place in and around the state.

It is not unusual for Russian activity to be detected in the ADIZ, the defense command said, and such activity is not considered a threat.

Indeed, there have been multiple such incidents in recent months. In February, U.S. jets intercepted Russian aircraft twice in one week. In both cases, the Russian planes again did not enter Alaskan or Canadian airspace. An intercept, according to NORAD, just references when an aircraft makes visual or electronic contact with another plane.

NORAD said in the news release announcing this week's detection that it uses "a layered defense network" of satellites, ground-based and airborne radars and fighter jets to track and identify aircraft.

"NORAD remains ready to employ a number of response options in defense of North America," the agency said.

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