Two Russian surveillance aircraft were tracked in the Alaska Air Defense Identification Zone on Saturday, according to the North American Aerospace Defense Command.

The IL-38 Dolphins remained outside U.S. and Canadian territorial airspace and were not deemed a threat, according to a Sunday news release by NORAD. Russian aircraft regularly operate in the area, according to the command.

An ADIZ is a stretch of international airspace where aircraft are expected to identify themselves in the interest of national security. The zone is not a formal agreement between nations and not always recognized.

The surveillance flight is one of several by the Russian military this summer that skirted international boundaries but drew attention from the U.S. and its allies.

On Thursday, a pair of Russian Tu-124 patrol aircraft made a circumnavigation of Japan, staying outside its territorial airspace, on the first flight of its kind in five years, according to Japan’s Joint Staff.

Japanese fighters scrambled to intercept and track the Russians.

In July, a pair of Russian bombers teamed with two Chinese bombers on a flight in the Alaska ADIZ, NORAD reported at the time. U.S. and Canadian fighters scrambled to intercept the aircraft.

The bombers, flying in the Alaska zone for the first time, came within 200 miles of the Alaskan coast, according to the Pentagon.

Also in July, two Russian Tu-95MS Bear-H strategic bombers made a 10-hour training flight international space separating South Korea and Japan, whose fighters rose to intercept them.

previous coverage

• Russian and Chinese bombers spotted near Alaska: ‘First time we’ve seen those 2 countries fly together like that,’ Austin says
• NORAD jets intercept 4 Russian and Chinese bombers off Alaska coast
• Russia says bombers completed 10-hour training flight between Japan and South Korea

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• Russia sends patrol aircraft around Japan as it trains with China on seas below