If I read the situation right we have this:
A fighter is launched to go sink a transport. The only legal landing zone would be if another battle is waged to clear a sea zone so that an aircraft carrier can move to retrieve the fighter.
This is legal, even if there is statistically no chance for the naval battle to be won and thus the carrier won’t be able to move to recover the fighter.
Because there is A chance the battle could be won, it might be 1 in 1,000,000 but it’s still a chance and therefore, the aircraft carrier DOES count as a legal landing zone for the fighter. Yes, this means you could attack 14 battleships, 3 loaded Aircraft Carriers and 12 submarines with 1 submarine, declare your submarine is commanded by Superman himself and thus will not die, thus allowing free passage for your aircraft carrier and then declare that carrier as the place you will land the fighter - should the fighter survive it’s engagement and it is 100% legal to do so. We all know that the fleet you are attacking with your submarine is going to hopelessly slaughter your submarine crew, but there’s that 1 in a bazillion chance your submarine could win and that’s all that matters to make the move legal.
That said, if you cannot move the carrier to recover the fighter, and there are no other legal places to land the plane, it is lost.