Doug-
OK, I've broken down and picked up GF2 for comparison with GF1. I'd been wanting to do this anyway, and this just gave me some incentive.
I think GF1's air rules could reasonably be grafted onto GF2. Obviously, all the air-to-air combat could be handled within the GF1 rules.
For WWI, at least, I think GF2 AA ratings could be used with the GF1 rules, if you didn't want to recalculate the AA ratings with the GF1 formula. The formulas are pretty close for the smaller AA guns, and only differ significantly for the larger AA guns that you'd find in WWII.
Because the GF2 hull boxes are calculated differently than the GF1 hull boxes, the damage done by GF1 bombs would need to be adjusted for attacks on GF2 ships. I've done some calculations, and I think an easy approximate conversion would be
(GF2 damage) = 1.5x(GF1 damage)
Round fractions up.
The deck armor rating in GF2 is intended for use with plunging fire, and so isn't really suitable for use against bombs. You could calculate a deck armor for defense against bombs using the GF1 conversion rules if you have access to a Conway's, etc. (Let's call that armor value "A", for Aerial defense.) I think this formula would get you "A" from the GF2 belt (B) and deck (D) values:
A = 2D - B - 1
I don't think you'd want to try to do anything really air-intensive with this, but for the occasional Zeppelin or or H.12 that's out scouting and gets closer to the enemy than anticipated, the GF1 pdf would get you air rules for $9.98.
I suppose I should emphasize that I haven't actually tried any of this.
-Eric
Edit: OK--I feel stupid. If you get GF1, just use the GF1 deck values instead of the GF2 deck values when rolling for bomb penetration. No conversion needed.