Well, after a few tries, I can say that, if you put Backfires instead SU24, they shoot from a very far distance (more than 30miles) and when all missiles are expended (4 each plane?), they return to base.
If you set the altitude of the SU24 very low, close to the sea, they can get closer to the objetive without being shooted, but not enought to shoot.
My next tries will be with various SU24 groups from different sides.