Why now? Was this a deliberate attempt to destroy a potential "threatening" alliance against ISIS? After all Russian planes attacking the Turkmen militia and flying near the border are indeed provocative for the Turks, but it is nothing new. Earlier fighter jets have not been attacked.
At least the Turkish military should have been restrained right now, where the powers could begin to collaborate in the fight against ISIS. The Russian plane could simply have been escorted back.
Or does Ankara regard the PYD as so dangerous that it will sabotage a joint fight against terror and a beginning peace process in Syria just to prevent the Syrian Kurds from being recognized as a part of it? Was it an attempt at diverting the attention away from ISIS to help Turkey's own interests?