Going to necro this as I have pretty much the same question.
This is the thread about AA rules linked above.
Will light AA just do no damage?
Also, what is the AA Value that gets shown in the unit design window when mounting AA? Is it the damage done to planes on hit? If so, it doesn't match the rules linked above, in my attached image the designing empire has a racial weapon strength of 8 and another one with 10 gets the same AA Values.
Does the penetration stat on AA only affect it's ground combat values and has no effect on shooting fighters?