That would of course be the same FSA that's backed by the US and the same FSA who is allied with al-Nusra with whom the group shares American and Saudi-supplied TOWs and other advanced weaponry(see here).
As The Telegraph notes, "Alwiya al-Ashar [who fight with the FSA] is one of around a dozen Turkmen groups fighting alongside Syria's rebels. It is linked to a Turkish and CIA-backed logistics supply programme that funnels a near-constant stream of small arms, ammunition, and cash for salaries to rebel groups across northern Syria. So just to be clear on what's happened here in case the gravity of the situation is somehow lost on anyone, a NATO member from whose airbase the US is flying combat missions, just shot down a Russian fighter jet and the US-backed, al-Qaeda aligned FSA has released not one, but two videos depicting their fighters dancing over the body of a dead Russian pilot while shouting "Allahu Akbar" and holding up the "we're number one" hand signal.
