Also, as Germany I tend to relax if I see Russia build fighters. Although that means Russia can trade increasingly efficiently, it still never exceeds the efficiency of the mass Luftwaffe I have, and every fighter built means a significantly less chance of Russia being able to actually move in to areas like Ukraine with enough defense to hold it. 1 fighter cannot even land immediately in a territory it just took, which is in very large contrast to 2 inf 1 art helping to hold the land it just took.
If Russia builds more than 1 fighter, Germany might be able to move in and Russia unable to dislodge a large force since they’re so busy increasing the efficiency of trading territories at the cost of land forces.