I think you might be conflating airforce with air defense. There’s not a lot of Ukrainian AF flights these days and when there is, it’s more often than not, one way (unfortunately) - and with loaned gear. It’s why they’re asking for F-16s and more AD.
It's hard to say that without having inside information. That Ukraine has managed to keep any of their aircraft flying in the face of far superior numbers is astounding. They are still managing to launch SCALP from SU-24m frequently (as frequently as the limited supply of these missiles allow). Considering they're probably outnumbered 5 to 1, that's either indicative of operational excellence on their part, or Russian inadequacy.