Air is way over powered when fighting against Navy. I had complete fleets of ships wiped out by a few air attacks. With no air losses from the enemy.
IRL Air is always most effective vs ground forces (google "iraq highway of death" if you want a perfect example)... any attempt to sink a fleet of 10+ coordinated modern warships would see at least 80%+ loss of aircraft in a real world scenario. By the time your close enough to shoot at them they can shoot at you, often with more effective and more numerous Anti-air missiles. The way it plays now its like the enemy is bombing unarmed cargo ships.
Anyway... just my 2 cents but if you want to nerf air I'd look at navy.
On the resistance side... I don't know about mechanics BUT I do know IRL the only real way to crack an underdog force in "fortify" mode is via ground forces. Lots of ground forces, normally in bloody street to street/village to village clearance operations. Maybe ground control could power up that way?