Logically, if any stats of units rise with each new model, the units are getting better right? If that is so, why do AA-Brigades and escort fighters give minus air defense? In my opinion the higher the air defense is, the more difficult it is to shoot down a plane, but why do aa and escort fighters give minus air defense ? Doesn't that make ground and air units with these attachements worse for aerial combat or did i misunderstand something here ?