Russian fighter jets invade airspace over Alaska. Two Russian planes entered an air defense zone outside Alaska airspace on Thursday.

It was the second time this week that such an incident has occurred, the North American Aerospace Defense Command NORAD reported on Friday. The flights were observed after four Russian aircraft entered the ADIZ on Tuesday, prompting NORAD, a joint US-Canada air surveillance and air defense body, to issue a similar statement. “These Russian activities in the Alaska ADIZ occur regularly and are not considered a threat,” NORAD continued.