When using planes for offensive purpose against a human opponent, in 99,5% of the situations you shouldn't use the attack button, but send them on "patrol" instead.
This makes air mechanics weird, unrealistic, hard to understand for beginners (for example they have to learn that all enemy units within the patrol circle sum up and defend as one stack) and not satisfying for experienced players. Always same-same: Build as many 6-fighters+6-bombers stacks as you can, then send them on patrol where the enemy has few AA; switch off your brain.

So please implement the following changes:
* Remove the 15min patrol timer - planes on patrol don't attack.
* Since that would make them too vulnerable during refueling (in particular against rockets), increase HP of refueling planes to 15 or 20.
* Since without patrol as attack command air would have one tactical option less, give +5 HP to both tactical and strategical bombers (i.e. tacs 25 and strats 35) and increase manpower cost of AA guns from 750 to 1000. So air vs. ground would stay balanced.
* Decrease tactical and naval bomber attack damage against air to 50%.
* Decrease strategical bomber attack damage against air to 0%.
* Increase strategical bomber defense damage against air to 150%.
* Increase fighter attack damage against air to 125%.
* Decrease fighter defense damage against air to 75%.

This would make patrol what it really was - a defense manoeuvre for fighters. And it would open interesting tactical options because then it sometimes makes sense to separate fighters from bombers.

Some other major results would be:
* You should only attack with planes that are based on an airfield either out of range for enemy bombers (otherwise they'd bomb you while refueling) or secured with sufficient AA (your planes can't fire while refueling, but the AA will, so losses would be high on both sides).
* Attacking targets underneath hostile patroling fighters practically never would be an option any more. You first have to shoot down the fighters. In other words: Gain air superiority, only then you can use your bombers everywhere.
All of that would be realistic, intuitive and tactically/strategically interesting.

Here I want to stick to my reasoning. Have in mind if patrol attack timer is removed, you would have to refuel every time you used your planes. So if refueling planes were left at 5 HP, it would be impossible to use them as long as your opponent has rockets. Also emphasis in planes vs. planes combat would be too much on catching the opponent while he's refueling. That would also be a strange game, then.

About strats you're just so fully right. I now changed that in my proposal. But the tactical and naval bomber unit in CoW I imagine to cover also single-propeller models, for which I wouldn't go so far. These indeed also were never used to attack fighters, but if my proposal was realized, also in CoW you wouldn't use them to attack mere fighter stacks. Anyhow would be much closer to reality than the current implementation, in which you always use all kind of available aircraft when engaging a battle against the enemy's airforce.

I now also simplified my proposal a bit, please read it again (everyone). But note I assume that patroling planes use their attack value for the free shot they have against an enemy air stack attacking a target in their patrol circle (of which I'm not sure). If they in fact use their defense value, that would also have to be changed to their attack value.