I'm not a pilot, though I'm interested in flying.
That said, I've heard (and asked) for more air support for Ukraine basically since the war started. I've read where it can take months for a tank crew to learn a new tank and operate smoothly and effectively as a team. Wouldn't training pilots to fly aircraft they've never flown before be significantly more difficult? I mean, sure, an experienced Ukrainian pilot could likely learn to operate the machine at a basic level in a relatively short amount of time, but the margin for error and knowing the capabilities and weaknesses of each airframe are critical for peak performance.
So unless someone is giving them soviet era fighters I'm not sure this is a really viable solution (again, I'm relatively ignorant wrt flying a jet).
The only other way you get foreign (such as US-made) air power into the skies over Ukraine likely requires foreign pilots who are well-trained in those jets, and I don't see anyone wanting to get into a direct hot-conflict with Russia.
No sarcasm, please show me where I'm wrong.