The strongest air force in the world is not Russia but USAF, in case u dont know. USAF is fighting ISIS and scores great results. Just recently they captured Sinjar, al Hawl, most of Ramadi, Tishrin Dam. They killed several prominent leaders and destroyed ISIS treasury with cash, which is a HUGE blow to them. Meanwhile Russians did nothing against ISIS except boming some grain silos claiming these are oil storage, damaging water carriers to civilians and blowing some trucks carrying fuel so people could warm themselves in winter.
Also when one side supports another it does not mean they are friends. Just common interests. Islamic Saudi Arabia supports secular Sisi against Islamic MB. Islamic Iran supports non Muslim Assad against Islamic fractions in Syria, Qatar and Saudis are allies in Syria but opponents in Egypt etc etc.