Flyable and non-flyable FM differences etc.

[SaQSoN]

Both flyable and non-flyable aircraft in the game use same algorithm for FM calculations. However, some non-flyable aircraft may have various FM parameters adjusted with less precision, then flyables. AI in most cases doesn't take planes to an extremes, like humans do, so looking at them from aside make their performance look realistic enough.

[The Stalker]

So basically the flight characteristics of AI only FMs are a bit more "raw" in terms of maneuverability, speed, stall, lift etc? As in more approximate than flyable ones?

[JtD]

More like they might be missing the proper frequencies for their oscillations, be a bit raw when it comes to damping, have unadjusted ground handling and things like this. It usually just is the real fine tuning that's missing, exceptions go both ways.