FMB Question - Fleet engagement UNwanted

[Racetrack]

Hi guys! I'm just making a mission in the Pacific..
3 huge fleet 2 USA and 1 IJN, I'm just wondering if there's any way to avoid the fleets to open fire against each other.
I placed the fleets 40-50 Km away from each other to avoid the problem of spending much time ( annoying problem ) to fly from Base to Objective.
I want the fleets to fire with AA against enemy planes and at the same time i DONOT want they to open fire with main guns against the enemy fleet.