You don't say which version of CFS this is. The AI flight model in CFS1 & CFS2 is not usually ideal for the Player aircraft or vice versa. Rather than try to use the same one for both (like the flyable defaults) it's easier to have special unflyable AI drone versions of 3rd party aircraft you wish to use for AI purposes. It's generally the same in FS2002/FS9.
That's close to what I wound up doing. I kept the .air file I'd adjusted for Free Flight
mode and readjusted a copy of it for use in CFS1 Single Combat. However, at the moment, I have to use one variant plane for Free Fight and the other for Single Combat; neither the AI planes nor the flyable one sit well on the runway with the .air file that's adjusted for Free Flight. There's not a huge difference in the entries but enough to make the difference. They fly well enough with either file, providing the AI planes don't smash up before you've gotten your flyable plane well on its way.

What I'm indicating here is that the same file I adjusted with the flyable plane in Single Combat is the same one the AI works best with. In Free Flight I'm all by my little (relatively) self, so I'm not referencing it to the AI in that mode, and with the Single Combat .air file the plane doesn't sit right.
