Thanks for the quick responses!

Here’s the situation.  Two French infantry sit on an American transport with no other French units in the sea zone.  The seazone is serviced by an unfriendly air base in a territory containing a German fighter.  If the French units attempt to perform an amphibious assault out of that sea zone, does that fighter 1) prevent an amphibious landing, 2) destroy the American transport with French infantry still on it, or 3) have no ability to scramble?

I know that friendly naval units are spectators when a power attacks, so the American ships should not participate in the battle.  If the American transport is not a participant in the battle, does that mean that the French infantry are stuck on the transport when there is an unfriendly air base servicing that sea zone?