I essentially don't, they just are too weak to make a difference, having a few planes for reconaissance is ok, but I have never built them for anything else.
Well now see... that's my point... there's nothing wrong with folks thinking like that, I'm just trying to make airpower
useful and/or
decisive, as it is/was in history... and the answer is
not more ground-based AA units... airpower is nerfed enough as-is, I'm trying to make it useful again and/or make the proper counters needed (your own air force instead of more ground-based AA units
should be the answer). I don't want to empower players with tons of ground-based AA units so they too can ignore airpower.
The "problem", if there is one, IMO is that it's currently polarized. Either the human has tons of airpower that overwhelm the defense, or the defense has tons of intercept that overwhelms a reasonable amount of air support. Thus the human shouldn't bother unless he goes whole hog and builds a ton of offensive air units.
I'm trying to change the way everyone thinks of airpower... it
should be important and decisive, especially by the time of WWII airpower... I am (in-fact) nerfing WWI fighters a bit, as I thought they were able to do too much (bombing cities and improvements is a bit much for a WWI Biplane), but I refocused it's mission as a true fighter and zeppelin buster (improved stats there). The addition and changes made to Carriers, Light Bombers and modern Jet Strike Fighters should encourage to all the importance of airpower (I'm hoping).
In my experience, I have seen the AI ignore Flight like the plague... at least as-it-is out of the box... I have been working to change that... while the AI is very good at spamming airships (as everyone knows and complains about), when it comes to flight, fighters and bombers, I've seen the AI avoid it and research everything but flight.
In my last few versions of the Wolfshanze Mod, I have been slowly bumping-up the importance of at least researching flight for the AI (an unannounced change... I'm sneaky like that). Default Civ4 gave flight a very,
very low importance for the AI to research it. I've been bumping that up until I see the AI start to research it a little more like it should... and in my current game I'm finally seeing the AI bite on it.
The human swamping the AI with airpower is something I'm trying to fix (I always did it myself)... the reason seemed that the AI wouldn't bother researching Flight, which I'm trying to fix. If I make the AI research flight, the human shouldn't be overwhelming the AI from the skies anymore (well, in an equal-footing situation)... as for the AI vs the human... well, I would think if the AI was blasting you from the skies a human would be able to make the logical conclusion what he should research next.
I'm hoping if the AI uses it, the human will want a counter, which is why I'm avoiding adding more and more ground-based AA units... the proper counter should be your own air force... I also moved some important units and wonders to Air Superiority as another incentive (especially to warlike civs... peaceful civs can ignore Air Superiority if they want... well, as long as the AI isn't going to town on you from the air).
I'm enjoying the changes to airpower (call me focused... maybe cuz I'm a USAF vet)... I hope you guys appreciate it as well... even if it makes some of you have to create your own airforces when before you would ignore it.