[dmix]

Pretty sure almost all of the functional ones were destroyed or were kept in such reserve for security they weren't being used.

[varjag]

No there are still tens of original UAF jets that by now clocked thousands of sorties. Sometimes they get shot down or otherwise lost and we get photographic evidence (tail number, sometimes even pre-war colors) that it's one of the OGs.

[greedo]

They're still flying SU-27 frequently, and those weren't replaced by donations.