Honestly, I'm with Jandor on this one. Garlean air superiority has been handled ridiculously badly, in-game. (Like most things Garlean, really, but for the sake of brevity I'll not get into that.) Back in the earliest days of 1.0, the first ads I even saw for the game featured ominous images of flying Garlean air units, striking home just how dangerous they were. Potentially a great set-up for an underdog victory - but really, you gotta show how the underdogs EARN that victory for it to really be satisfying!

It really wouldn't even be all that difficult. Even without resorting to Primals or dragons, the alliance has resources that could theoretically be used to check Garlean's air superiority. Ishgard's dragon killers are one example, certainly, but thaumaturges on airships could certainly work, as well. I'm guessing that the Ironworks could help out, as well; even if Cid is against producing weapons, he could provide other tools, from things a simple as personal flying machines to more complex items like jammers to disrupt the Garleans' electronics.

Maybe the Alliance has these things, maybe they don't, but the important thing is we never SEE this. Our big battle cutscenes are just about always on the ground, nary a gunship to be seen. The only times we DO see Garlean air is when we have something new specifically to counter it, like Ysayle's Shiva summon or Hien's Yol armada.

It's possible that the Garleans keep their expensive air units in reserve BECAUSE they know the Alliance can counter them, but this is purely speculation, and has no reference in-game. Just one of the gunships we saw at Castrum Meridanum would have savaged even a vastly numerically superior ground force. Air superiority is a complete and total game-changer when it comes to battlefield tactics, and it boggles the mind that the Garleans don't use it more. It shouldn't be up to us to find reasons why they aren't used.