Russian Fighter planes flew in international Air space around Gotland and Bornholm.
International air space, i.e. it doesn't belong to anyone and anyone can fly through it without needing to let nearby countries know about it.
It is a non-event. If they fly into Danish or Swedish air space, then it will be an incident, but until then it is just complaining about someone doing nothing wrong.
The same goes for when they flew near the UK recently, near but not into our air space..
Then why do it without transponderes active?
Why did they deactivate them?
Simulated war/combat condition. This is the risky part because, in wartime civilian air traffic would be grounded but, in peacetime you cannot ground civilian air traffic and you're flying in crowded airspaces without coordination with ATCs thus increasing the risks to safety (e.g. collisions).
Just funny how we have to send fighters to intercept them so they wont enter Danish Air space all the time.
And its everytime we do it.
Its to provoke, not to train.
Air Forces trains everyday, often simulating war/combat condition; however, if you train this way in periods of international tension near territory of countries with each party seeing the other as potential hostile a party could interpret such training as a provocation, Russian see NATO patrols as provocation, NATO see Russian ones as provocation.
Makes you wonder though, why would the Russian aircraft be "invisible" to civilian radar?
Civilian ATC radars are mostly not real radars at all but receive
aircraft transponders' signal. Turn an aircraft transponder OFF and the same aircraft will be visible only to Air Defense (a.k.a military) radars and a few primary ATC radars (the real civilian radars). In this condition quality of ATC air picture degrade a lot and workload for air traffic controllers skyrocketed up; thus, risks of accidents go up as well.