You know, that's something that's always bugged me. I hate trying to figure out if it was just bad luck that my bomber got screwed this time or did the other guy invest in AA tech.
I think after the bombers go in the AA level should pop for a player to see. It's not like all that flak is going to go unnoticed. Now, just to make it interesting, make it so can you move AA resources for a price from city to city. Cuz then you could really screw with the other guy's head.