U.S. military fighter jets were dispatched on Tuesday to follow a Russian reconnaissance plane flying close to Alaska, as reported by the North American Aerospace Defense Command (NORAD).

This marked the fourth instance in under a week that NORAD has identified and monitored a Russian IL-20 COOT, a reconnaissance aircraft from the Cold War era, within the Alaskan Air Defense Identification Zone (ADIZ). This zone is international airspace where aircraft must be swiftly identified for national security purposes, according to NORAD.

The same type of Russian aircraft flew over the region on Aug. 20, Aug. 21 and Aug. 24, the military command said. 

In each of the four instances, NORAD responded with its own fighter jets to track the spy plane.

In July, NORAD shared images of U.S. fighter jets intercepting Russian military aircraft inside the ADIZ. 

Additional sightings of Russian aircraft in the ADIZ occurred earlier this year in April, and twice in February. During these incidents, NORAD stated that an F-35 Lightning II fighter jet intercepted two Russian Tu-95 bombers and two Su-35 fighter jets in the ADIZ.

In all these previous instances, NORAD said the Russian aircraft remained in international airspace.

Earlier in January, NORAD said it sent a combat air patrol unit to monitor multiple Russian military aircraft activity in the Arctic.