Possible insight into air bug?
As Germany in the 4 player GC (demo). I was able to perform recon missions for the first part of the game. With tech enhancement events I got lucky and completed research on light machine guns first. At that point I was still able to pertform recon missions and my planes engaged and shot down enemy aircraft. A few turns later France aquired light machine gun tech. As soon as France did so the recon mission would still happen, but whenever the planes engaged, the French planes would never engage. I could move my planes in and out of the front line to reset the engage button. But the French planes would never engage. Since you can't proceed until after the first engagement. Had to restart the game. Tested it several times with the same results.
Not sure if it helps. But thats what I am experiencing in the Demo.
Nial