Photo of Russian Sukhoi Su-24 Fencer attack planes near Idlib in Syria.

It is vital note that Russian Air Force  deployed   28 combat planes ( 4 Su-30SMs, 12 Su-25SMs and 12 Su-24s )to Syria.

Based on the couple of videos emerged so far, it seems quite likely that the 28 aircraft deployed to Syria in four-ship formations led by Il-76s, Il-78s and (maybe) An-124 airlifters, in radio silence and shadowing the accompanying cargo/tanker planes to remain “stealth” to radars along the route.