-single player- scenarios- marine battle , The airplanes are on an island
while the enemy is on another isle across a small stretch of water. Enemy is isle bound and my planes wont reach over their isle to provide
my troops cover. What am i supposed to do? no carrier in sight. my landing troops get pounded every time trying to invade enemy isle w/o support.

yaaaaawn
suppose you mean the "marines scenario".The enemy on island is very weak.So what for do you need those aircrafts? Scenario can be easily won by most stupid direct assault without any air support.
replay attached

You can conceivabley use the airplanes in this scenario. You need to take the capitol as early as possible, then fly the planes in to your newly aquired city. Not likely that this will be early enough to really help though.

you don't realyl need the planes for support.

This scenario is a little bit difficult for a newbie. What you must do is 1) first destroy the Missile Launcher, 2) take the Capital soonest, and fly your Air units over for defence.

just a little notice - while looking at my replay you probably notice another example of AI's stupidity.AI knows that destroying transport is a good idea.But in situation when transport can not be destroyed instantly AI still shoots at it (though those shots can be used to destroy other targets)