Yeah, sure they have. American aircraft are nothing like Soviet frames. And two big glaring problems. Where did they base? Where do they takeoff and land? Because if it’s in Ukraine, that place is going to get annihilated with cruise missiles. If it’s in Poland, that’s NATO attacking Russian forces. And then the few that manage to make it to the air are in S400 range anywhere in the battle areas…
Ukraine still flies mig 29’s, su27’s, su25’s and a bunch of choppers that according to the Russian MO counts have been annihilated many times over since February 24.
Both sides have managed to create air denial zones with SAMs. Ukraine even managed with western help to integrate the HARM missile into their 29’s. They will do so much more with HARMs on their native F16 platforms.