Here's how an air war between Russia and the US in Syria would go down
But while Russia has some advanced surface-to-air missile systems and very agile fighter aircraft in Syria, it wouldn't fare well in what would be a short, brutal air war against the US.
The US keeps an aircraft carrier with dozens of F/A-18E fighters aboard in the Mediterranean about all the time and hundreds of F-15s and F-16s scattered around Turkey, Qatar, and Jordan.
According to Omar Lamrani, a senior military analyst at Stratfor, a geopolitical analysis firm, Russia has "about 25 planes, only about ten of which are dedicated to air superiority (Su-35s and Su-30s), and against that they'll have to face fifth-gen stealth fighters, dozens of strike fighters, F-15s, F-16s, as well as B-1 and B-52 bombers. And of course the vast US Navy and pretty much hundreds of Tomahawks."
"Russians have a lot of air defenses, they're not exactly defenseless by any means," Lamrani told Business Insider, "But the US has very heavy air superiority." Even though individual Russian platforms come close to matching, and in some ways exceed the capability of US jets, it comes down to numbers.
So if Russia did follow through with its threat, and target a US aircraft that did not back down West of the Euphrates in Syria, and somehow managed to shoot it down, then what?
"The US coalition is very cautious," said Lamrani. "The whole US coalition is on edge for any moves from Russia at this point."
Lamrani also said that while F/A-18Es are more visible and doing most of the work, the US keeps a buffer of F-22 stealth jets between its forces and Russia's. If Russia did somehow manage to shoot down a US or US-led coalition plane, a US stealth jet would probably return fire before it ever reached the base.
At that point the Russians would have a moment to think very critically if they wanted to engage with the full might of the US Air Force after the eye-for-an-eye shoot downs.
If US surveillance detected a mass mobilization of Russian jets in response to the back-and-forth, the US wouldn't just wait politely for Russians to get their planes in the sky so they can fight back.
Instead, a giant salvo of cruise missiles would pour in from the USS George H. W. Bush carrier strike group, much like the April 7 strike on Syria's Sharyat air base. But this time, the missiles would have to saturate and defeat Russia's missile defenses first, which they could do by sheer numbers if not using electronic attack craft.
Then, after neutering Russia's defenses, the ships could target the air base, not only destroying planes on the ground but also tearing up the runways, so no planes could take off. At this point US and Coalition aircraft would have free reign to pass overhead and completely devastate Russian forces.
Russia would likely manage to score a couple intercepts and even shoot down some US assets, but overall the Russian contingent in Syria cannot stand up to the US, let alone the entire coalition of nations fighting ISIS.
Russia also has a strong Navy that could target US air bases in the region, but that would require Russia to fire on Turkey, Jordan, and Qatar, which would be politically and technically difficult for them.
This scenario of a hypothetical air war is exceedingly unlikely. Russia knows the numbers are against them and it would "not [be] so easy for the Russians to decide to shoot down a US aircraft," according to Lamrani.
And Russia wouldn't risk so much over Syria, which is not an existential defense interest for them, but a foreign adventure to distract from Russia's stalled economy and social problems, according to Anna Borshchevskaya, an expert on Russia's foreign policy in the Middle East at the Washington Institute for Near East Policy.
"Russia is not a great power by most measures, like GDP, population, living standard," Borshchevskaya told Business Insider. "Russia has steadily declined. It's still a nuclear power, but not world power."
In Syria, "a lot of what Putin is doing is about domestic policies," said Borshchevskaya, and to have many Russian servicemen killed in a battle with a US-led coalition fighting ISIS wouldn't serve his purposes domestically or abroad.