I want to now how to attack air units. I can't find how. Please help.
1) Use fighters, they need to be in adjacent hexes.
2) Use AA (anti-aircraft units). Some AA units need to be in the same hex, and some can also be 1 or 2 (or maybe even 3) hexes away.
Also if there is a ground unit below the air unit, you'll have to move the cursor to the upper part of the hex. And if you have wheather on and it's raining or snowing forget it, air combat is not possible then.