Recently, Michael Kofman and I published an article arguing that Russia’s claimed withdrawal from Syria is not really a withdrawal, but rather a public relations move to normalize Russian military presence in Syria for the long term. Events over the last 10 days have confirmed our analysis and also provided more details on the air forces that Russia is continuing to maintain in Syria. A photo made by the French Centre National d’Etudes Spatiales and distributed via IHS Jane’s shows that as of March 20, there were still 12 Su-24M bombers at Hmeymim, as well as four Su-34 bombers, three Su-30SM fighters and three Su-35S fighters. Zero to three additional aircraft may have been out conducting airstrikes, for a total of 22-25 remaining Russian fixed-wing strike aircraft in Syria. There were also 14 helicopters, including two Mi-28Ns and two Ka-52s.
This means that in the first week after the withdrawal was announced, Russia pulled out three Su-24Ms, four SU-34s, all 12 Su-25s, and four Mi-35M helicopters, while adding at least two Mi-28N and two Ka-52 helicopters. The photo also shows IAI Searcher Mk2 Forpost UAVs.
In other words, the current size of the Russian air presence at Hmeymim is comparable to what Russia had at the start of the operation, minus the Su-25s, but with the addition of Su-35s.