Russia has the best anti-air defenses in the world. Period. Also, the F-16s will presumably have to land at some point. When they do land, they can be hit with Russian missiles. Also, I feel like it probably takes more than 6 months of training to become proficient in flying and fighting in an F-16. You might be able to keep the thing from crashing into the ground, but beyond that?

I'm sorry, we've all seen this argument before. It was the Bayraktar drones and Javelins, those were the gamechangers. Then the HIMARS. Oh, but the M777s and Caeser howitzers, that'll win them the war! Then the Leopards and Bradleys, which now lie destroyed in minefields, and the Patriots, which are hit by hypersonic missiles (with liberals argue that due to Newton's Third Law, if you think about it, the Patriots also hit the hypersonic missiles). Now it's the F-16s and the Abrams. It's been a never-ending treadmill of the West bringing out weapons and equipment, promising every single time that THIS will be the thing that makes Putin pee his pants and surrender to the Ukrainians. It hasn't happened, and given the appalling deaths and casualties and destruction on the Zaporozhye front these past two months with Ukraine's third army being ground down to scrap, it doesn't seem like it ever will happen.