Russian military jet downed by Turkey

[Husar]

Fair point, but this mess is still 50% Rusiia.

That fits very well with their similar political leadership, doesn't it?
It's like a clash of two hard-headed conservatives...

Russia has been skimming the edges of NATO airspace since forever. I remember that when the sanctions were raised over the Crimea annexation, Russian bombers flew over the Pacific and reached California. They congratulated the US fighter jets sent to intercept them (it was the 4th of July) and turned back. They were 20 kilometers from US airspace. Putin likes taunting the US like that. This skimming over the edge of enemy airspace was a common drill during the cold war I hear.

Can't imagine anything going wrong, seems like a brilliant plan.

Eh, well, that's a really bad comparison for a number of reasons.
First of all, I'm pretty sure that NATO also operates or exercises somewhere near the Russin border once in a while, the SAC always had planes in the air ready to head to Russia real quick and bomb a city or two. As for real danger, they don't necessarily have to enter enemy airspace if they have cruise missiles.
Secondly, as you say yourself, they fly close to it, they do not necessarily enter it. If we are being so technical about lines, the Russians never seems to cross the line in Europe so what they do is perfectly fine and happening in international airspace.
Thirdly, Syria is a war zone and Europe and the US are not, these Russian visits are almost like games, in 70 years or so I don't remember anything "going wrong" (meanwhile the US lost a nuke or two over its own territory...) and the pilots almost act like friends unless the Euros happen to be super serious.

And lastly, how can you warn someone ten times if it takes them only 7 seconds to fly through?
Yes, it was partially the fault of the Russians for flying through in the first place, but I assume the Turkish pulled the trigger more out of spite than any legitimate safety concerns.