Russia’s Antonov An-124 unloading in Latakia airbase
Incredible news for anyone who still remembers the low-point Russian-Turkish relations were at in late 2015. Turkey has quietly opened its airspace for transport planes of the Russian military headed to Syria.
Where in November 2015 Turkey shot down a Russian Su-24 strike jet because it allegedly strayed into Turkish airspace for a few seconds, the Russian forces in Syria are now being supplied by planes traversing the width of Turkey.
Also, recall that in 2015 in accordance with US wishes Bulgaria and Greece denied the use of their airspace even to Russia's Emergency Ministry Syria-bound humanitarian flights. The US can't be happy with Turkey right now. (Incidentally it is not.)
Moreover, visiting Russia today, the Syrian president Bashar al-Assad likewise flew over Turkey.
This would have been completely unthinkable in 2015, but something crucial happened in between - Turkey has completely given up on the previous goal of seeing a Sunni Islamist rebellion topple the Syrian government. It has resigned itself to the military victory of Russia and Damascus over the jihadis it once lavishly backed.
Instead it has limited its ambition in Syria to merely limiting as much as possible the self-rule and power of Pentagon-backed nationalist Syrian Kurds - a goal which does not run contrary to what the Syrians and Russians are aiming for.
It makes sense for Turkey to now try to both boost Moscow and Damascus against the US-Kurdish partnership in Syria, and to ingratiate itself with them seeing how ultimately Turkey, a home to over 15 million Kurds, is much more nervous about Kurdish nationalism than Syria where they make up less than 10 percent of the population, or Russia. (Russia in particular could obviously very easily live with an autonomous Syrian Kurdistan.)
Ankara wants Russia to take into account its wish for Syria to keep the Kurds as isolated as possible, but if Erdogan is to have leverage he must show his cooperation can be highly beneficial for Russia - more so than a settlement with the Kurds.
In any case, the fact Russian cargo planes are now flying to Syria over Turkey gives us an excellent indicator of Russian-Turkish relations and the trust Russians put in them. Should Russians start flying over Iraq and Iran again instead, it will be a sign the relationship is going bad again.
Comment: Russia, Iran and Turkey recently held trilateral talks on Syria which Lavrov described as "very useful", and added they had all "agreed on key issues". Furthermore, Erdogan´s chief advisor Yalcın Topcu recently declared: "The presence of the great Turkish nation in this institution [NATO] has become questionable," and he branded NATO's behavior towards Ankara as "brutal and dishonorable."