Inertia is really the wrong concept. It might be a language barrier, but a phrase such as "accelerate in its frame of inertia" has absolutely no meaning to me. Acceleration is a change to velocity, while inertia is a description of how an object does not change without a force applied to it. A model doesn't have any more or less inertia within the medium that surrounds it. The only way that could come into play is if the model hits the ground, but even then that's really a measure of kinetic energy rather than inertia. The kinetic energy is greater when flying with the wind, as the component speed of the wind is added to the speed of the model. Into the wind the kinetic energy is less, as you subtract the component speed of the wind from the speed of the model. That's just an overly complicated way of saying groundspeed.

What- -exactly- - are you trying to say when you talk about inertia?