Unconfirmed reports indicate Turkey may have shot down a Russian fighter that violated its airspace. If you've been watching the news, there have been two recent reports that Russian fighters (or possibly Syrian ones -- it is unclear that Russia is operating MiG29s in the area) had locked on to Turkish fighters for extended periods this last week. Turkey's patience with such antics may have worn out.
Turkey, where bombs targeting pro-democracy protesters killed at least 97 today, is dangerously unstable and can ill-afford to appear weak. Russian provocation may have run up on a target that has less to lose from fighting back than from not fighting back. Still, Turkey is a NATO "ally" -- in fact, they've stabbed us in the back several times -- and we are at least in theory obligated to respond to an attack on Turkey as we would to an attack on the United States.
Oh, by the way, remember how we discussed a few months ago how the US would be without an aircraft carrier in the region for the first time in recent history? That aircraft carrier just left the area. Russian naval vessels have been pouring in, however.