Well I'm now finishing turn 12 of a new game. Main difference I put a lot into my fighters, maybe too much (15 fighters. I actually got a few less tactical bombers than my previous try. So the result has been that I was able to take on the Polish Air and prevail much more rapidly.
Interesting conversation you all have been having about this. For me the problem was more the number and strength of the Polish bombing. They would hit my tanks very effectively taking 3 and more strength points often. So I used the fighters more often to attack the bombers than to attack their fighters. I di do that as well of course. To take out a full strength bomber usually took at least 3 and sometimes even 4 fighter attacks. Same on their fighters. So I don't agree that their planes can easily be taken out.
The AI used their fighters well, they would normally go after my tactical bombers left hanging out there after they attacked on my turn.
I also have found the rain turns can complicate things a bit on the air war.
Anyway looks like by about turn 10 because of the heavy investment in fighters they are down to little air power unless they have some hiding out.
Ground war still going strong, even on turn 12 they are still attacking me and they have conducted some impressive offensive operations. My losses have been higher than I would have expected for this scenario. Seems a bit unreal to be honest. Although my offensive struggled many places from turn 10 to 12 things finally began to open up for me. Because of my experience in a few other scenarios I still worry that suddenly I'll be hit with a major tank offensive as I make the mistake of approaching one of their victory hexes

I guess time will tell. At least I'm still in the fight on turn 12.