NATO has been buzzing the borders of Russia all my lifetime with aircraft erc and beyond (Gary Powers anyone?) I doubt they ever stopped and have moved onto drones by now.
Even in Cold War Berlin each side tried to test out the limits of the other although the Red Army was allowed into a couple of places in West Berlin by agreement like a war memorial.
Both sides have been chancing their arm most of my lifetime. We get reports of Russian planes and ships round here all the time. The west does it to them as well... and it is no secret that British and American folk have been involved in the Ukrainian conflict. It allows both militaries to justify their spending so it is mutually beneficial as well as being brinkmanship.
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