@Brian1234 As your question is neither about the Website nor the Forum itself but about a specific game edition, I have moved your topic to the respective forum category.
The answer to your question is: The IC built-in AA fires against strategic bombing raids only.
See the unit characteristics on page 23 of the rulebook. Here it says:
“Cannot Attack, Defend, or Move: An industrial complex cannot attack, defend, or move. It cannot be transported. It is not placed on the battle strip.”
and later:
"Air Defense: Industrial complexes can defend against a strategic bombing raid. Before bombers can attack a targeted industrial complex, they will be fired on by the built-in air defenses of the industrial complex. "
Welcome to the forum.