You have to shoot down all the transport planes before they reach their airfields, which is right about in the center of the map. Keep your wingmen with you and then tell them to attack the enemy when you reach the first group. Shoot them all down as quickly as possible. Regroup your wingmen and then haul ass to the next group, the yellow dots. Keep doing this till you get them all.

Use the Search mode on this site and look up hornets nest. You will find many threads on this battle.