I have the Combat Jet Trainer mod for CFS2 featuring the L-39. I have modded one of the L-39's so that it shows up as an AI aircraft so I can go L-39 against L-39. The problem is that when the AI is flying an L-39, it's completely lame. It just flies straight and eventually flies into the ground. If I happen to be in it's path it will take a shot at me but it won't try to pursue at all. What do I need to do to make it try to chase and fight?

You guys will never really understood this program AI. You are not dealing with modern planes here folks. You expect quick responce and you will not get it. But if follow prop planes and know the history of World war two Aviation you will start understanding its behavior better. That been said, no sim AI will ever be  perfect. They all have their defeciencies.

Please down load this tutorial from Coyotes and see if it will help you http://www.sim-outhouse.com/index.php?lloc=downloads&loc=downloads&page=info&Fil...

Some other things to take notice to is...out side of how the AI functions when fully optimized like something similar to the stock A/C. The way the AI reacts and performs is not only based on the hardcoding but the plane.  Most of the jets are made with the player only in mind. Takes a bunch of tweaking to get the AI to work functionally, like not drop out of the sky, use it's moving surfaces (even flaps), drop weapons properly.  Things like the center of gravity and where the weight is set (like the pilot) effects the performance....and etc.

yeah sorry to rant...

http://simviation.com/cfs2mod16.htm

check out Tango Romeos A-4s for an example for tuned AI jets.