If the only attacking air factors come from PARA units, does the attacker still roll against defending air units? It's possible the attacker could hit if the defending air units have "+" triangles, even though the attack strength is zero.
The map's phrasing about PARA units suggests they can only be damaged, but it's not really clear.
Thanks for this Drake, I had to look it up myself. The rules on this point are:
"6. Resolving Combat Rounds, update this paragraph.
See the specific section for each type of Round to determine your total attacking Factors. In all cases, if any of your units have 1 or more printed Factors of the type for that Round, then the minimum number of Factors you can have after all modifications is 1."
What I intended, but did not state, was the corollary:
"If none of your units have 1 or more printed Factors, then your side does not roll."
So please consider that added, and I'll put it in the Errata. No, the PARA does not shoot back.