Yesterday, Turkey shot down a Russian fighter plane that allegedly crossed into Turkish airspace. The Turkish story on this incident is more than a bit doubtful (for instance, it alleges that 10 warnings were given and ignored by the Russians, but also maintains its airspace was violated for 17 seconds). But whatever the truth of the allegations, it cannot be disputed that the Russian plane did not pose a threat to Turkey. Russia has been flying sorties over targets in Syria for some time now and still has not struck any targets in Turkey. Thus, it is worth wondering why the Turks were so trigger-happy to shoot down a Russian plane, based on what is, at worst, a technicality.
For more insights on this question, I recommend the analysis of Philip Giraldi at The American Conservative. He discusses the circumstances surrounding this event in more detail and speculates on the likely rationale of the Turkish government:
Ultimately, this event appears to be a manifestation of some of our worst fears about the convoluted Syrian policy. America and its allies have effectively prioritized unseating President Assad over fighting ISIS. Thus, they have been indirectly or directly backing "moderate" rebels in Syria, many of whom ironically share virtually the same ideology and anti-Western sentiments as ISIS. However, this backing of the "moderates" puts the US and NATO at odds with Russia, who is supporting Assad and quite reasonably considers many of the "moderates" to actually be Islamic terrorists. This all has led to unnecessary tensions between Russia and the Western countries, who all share the goal of defeating ISIS.
Given all the complexities that unfold in a war, a direct incident between Russia and the US or its allies was virtually inevitable. This event is fulfilling that inevitability.
Now we must also consider what happens next? Will this escalate into a pointless and destructive conflict along the lines of World War I, since Turkey is, after all, a NATO member? Or will cooler heads prevail?
Thus far, Putin has condemned Turkey and (justifiably) accused them of being "accomplices of terrorists", but has not made any serious moves towards further escalation. Meanwhile, the Obama Administration appears committed to blaming the victims and playing stupid--claiming this is the result of a flaw in the Russian strategy of targeting the moderate opposition. On the plus side, even Obama is not overtly calling for an escalation with Russia at this point. We should be grateful the situation has not spiraled out of control yet, but we are from in the clear.
As a practical matter, we should also be very relieved that it was a Russian plane that got shot down by NATO instead of the other way around. Thus far, Putin's response has been admirably restrained on this issue. If it was a US fighter pilot that got killed because of deliberate fire from the Russians, I posit that American politicians would already be talking openly (and excitedly) about World War III.