In air battles some of the most annoying AI targets are the bunkers(dropping bombs are ineffective unless they are really strong or it is a direct hit).
In real life, AP bombs and incendiary bombs can destroy bunkers. AP bombs i dont know, but when i played a dynamic campaign in battle of britain(on the german side), when i dropped an incendiary bomb it was ineffective.
AP - Armor Piercing → you need direct hit aswell.
And incendiary → it’s dropping some kind of fuel and ignite it
A bunker is most of time damn thick → no effect on the inside.