If you look at a map (go ahead and go to maps.google.com and look at a map of Turkey and the surrounding area) one can surmise that this incident is about a lot more than just a Russian plane going through Turkish airspace.   In 2008, there was a Russian incursion into Georgia, which, if you look at the map, is right on the Turkish border.   Then, last year, Russia invaded and annexed the Caucasus, which, if you look at the map, is right across the Black Sea from Turkey.   Then, this year, Russia enters the conflict in Syria and bombs ethnic Turks which Turkey is allied to in the Syrian conflict.  

 

So now, a Russian bomber is in Turkish airspace for just a few minutes and the plane is just one mile within Turkish airspace, and the Turks shoot it down.  

 

This tells me this is about a lot more than just a violation of Turkish airspace.   The Turks are majorly PO'ed about a whole of stuff with the Russians and it is possible they just decided it was time to do something.  

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