My recon planes are always shot down!

[Imp]

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IMHO it would be more realistic with air attacks taking place before the battle than during it. Though the present effect that players have to think about AA defences and integrate them in their battle plan is nice.

Takes it out of the scope of the game but as has been said air is mainly used in rear areas vs supply & if possible nice juicy targets such as units moving to position in columns.
Air attacks would then just become a random pre battle unit destroyer.
You buy 10 tanks & only 6 turn up.

Even with the advances of today I would say airs main roll is taking out infrastructure & support, look at Dessert Storm as an example they were surprisingly ineffective vs dug in units. Main effect was probably harassment & hindering along with a big drop in morale.