Russia struggles to dominate Ukraine airspace; What happened to the bombers?

Military experts are perplexed regarding Russia's use of Air Force in the first 7 days of Ukraine invasion. Before the invasion, there were fears that Russia would quickly mobilise airpower & dominate Ukrainian skies. Russia hasn't engaged entire airpower, but kremlin would've surely predicted airspace domination by now. Despite the huge numerical advantage that Russia's air force enjoys, Ukrainian jets continue to fly.