Turkey says one of its fighter jets was shot down by Syrian air defenses over the Mediterranean today, a potentially alarming development as Syria's civil war is deepening and signs are emerging that Turkey is assisting the arming of that country's rebels.

Leading Turkish daily Hürriyet quoted an "official" source as saying Syria shot the plane down and that the two pilots were successfully rescued at sea. The Turkish government news agency Anatolia said the plane was an F4 Phantom, a US-made fighter that debuted in the 1950s and is often used for both bombing and reconnaissance. Turkey's fleet of F4s have been upgraded over the years with the assistance of both the US and Israel. Anatolia quoted Turkish Prime Minister Recep Erdogan as saying Syria has apologized the incident.

While there's no hard evidence yet that Syria shot the plane down, it's safe to assume that Turkey has been intensely monitoring developments in next-door Syria with every resource at its disposal, with thousands of Syrian refugees having poured into its territory, and elements of the loose-knit Free Syrian Army operating from within Turkish territory.

The chance this incident will lead to a major escalation in the conflict – with Turkey overtly fighting the Syrian regime of Bashar al-Assad – is extremely remote. Turkey isn't eager for war with Syria, and vice verse. President Assad has his hands full fighting his own people.

But the loss of the plane is a reminder of how hot the situation is becoming, with Russia having claimed it's rushing more air defenses to Syria to help its ally protect itself from outside interference. Jostling for supremacy over Syria's skies, if only in the interests of spying and collecting information, is likely to intensify, making future incidents rather more likely than not. While the events today are no tipping point, future ones that result in the death or capture of pilots could prove to be another matter entirely. Earlier this week, a Syrian pilot flew his Russian-built MIG-21 to Jordan and defected.

Turkey does frequently conduct bombing raids inside another neighbor – Iraq. Kurdish separatists from Turkey shelter in that country's autonomous Kurdistan and often stage attacks on the Turkish military across the border, usually drawing reprisals. Earlier this week, Turkish warplanes pounded what the government said were rebel camps inside Iraq, after an attack on a military base in Turkey left eight Turkish soldiers and over two-dozen Kurdish rebels dead. The country is unlikely to be looking for another front to fight on.

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Inside Syria, the war is set to drag on. An unarmed UN mission to monitor a cease-fire that was agreed to in April, but never adhered to, has been suspended. Norwegian Gen. Robert Mood, the leader of the mission, was in New York this week and all but conceded that it has failed and an adjustment of approach is needed. With reports of better armed rebel groups, financed by Qatar, Saudi Arabia, and Turkey, a quick resolution to a war that has displaced hundreds of thousands already is not on the cards.

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