You mean if you have an ally’s fighter on your carrier as you move into combat with it? This is a fascinating question. I think that the fighter can’t take part in the battle in any way, including as fodder. Since the fighter is cargo on the carrier, I would treat it like any other cargo on a transport, since it’s basicly the same thing except with a fighter. Since the ally’s fighter cannot attack with your forces and it didn’t take off before the carrier moved, it must be considered on the carrier if it sinks. “If the fighter doesn’t take off before you move the carrier, the fighter is treated as cargo for the remained of your turn and may not fly, fight or be used as a casualty” (p. 32)