I'm pretty sure I've seen this handled before, but can't remember the answer. There are two situations I'm looking to be clarified.
1) There is a Japanese aircraft carrier with 2 fighters and transports off the coast of Japanese controlled Hawaii. USA attacks with submarines and loaded transports to naval invade Hawaii. Once the Japanese aircraft carrier is destroyed, what happens? Do the planes immediately land on Hawaii and then take part in defending the naval invasion? Or do they continue to fly in the air and crash in the water if USA successfully liberates Hawaii? Or does the presence of the fighters keep the USA transports from landing at all since the Allied subs can't destroy them?
2) There are USA subs and transports off the coast of Allied occupied Hawaii. Japan attacks with subs and loaded transports. If the USA subs submerge, are the USA transports automatically destroyed and can Japan invade Hawaii?
1) USA transports die, Japan fighters land on an adjacent allied controlled territory (or die). in this case they land on hawaii
You gotta clear the sea zone first for amphibious assault (or lose the transports) and since submarines cant kill air units you need something else to aid in escorting the transports (air units of your own or surface warships)
This also is true if he has fighters on the island and an airbase, he can scramble into the seazone and defend against any invading ships (escorts) and kill your transports if he kills your escorts or if you dont have escorts (or if you only have subs) then his planes kill your transports before they unload
2) Japan attacking USA so yes the USA transports die to Japans submarines, yes Japan can then conduct amphibious assault because Japans transports are escorted and USA submarines have declined to defend. (lets say USA subs dont submerge...then a battle ensues between USA subs and japans. If USA subs win then Japan loses their transports before they unload, if it is a tie or Japan wins then Japans transports can unload)
Hope this helps