The airplane visual is designed with Metasequoia LE and saved as an .mqo file and a directX .x file.
The .par file stands alone, but is related to the airplane visual.
The best thing to do is copy an existing .par file from another model that flies in the same class
as your model and then edit it using a .par editor to fit your model exactly.
Files usually used by and FMS 2.8 model are:
.mqo - 3D MetaLE model
.x - DirectX export from MetaLE
.wav - Sound file for the model's motor sound
.par - parameter file edited for both flight physics, collision points and wheels
.bmp - image map for the 3D model (256x256, 512x512, 1024x1024)
_prv.jpg - preview of model used in FMS model selection
_readme.txt - model information, author, links to model site, etc.