"Nothing to do with lag. 2 aircraft = speed, trailer dives around 1000 feet to pick up speed. Closes with front aircraft, but is below, when in range pull nose up and take shot, the aircraft will start droping back again as it climbing. "
I get it now. I was thinking it was an energy thing. I see now its an geometry thing. Its sort of like splitting the distance between the horizontal and vertical planes. Plane A is 1000 yards behind plane B and coalt. Plane A dives and is 500 yards below and 500 yards behind plane B. By splitting the distance between the horrizontal and vertical, plane A has a shot opportunity of 500 yards. As he approaches co alt the distance will get longer again as the distance returns to one plane (ie horizontal plane). Got it !

Seems though, the faster the planes are, the less attractive this option would be as over certain speeds, a lot of E would be wasted and negate the advantage of putting the distance in 2 geometric planes.