Hi there if you have some old GMX models you can convert it to Blender …
I have do it with this manual very easy.
First install the fs2004 sdk gmax setup (we only need the folder plugins). Copy all files from the sdk folder plugins to your main gmax …/gmax/plugins folder.
Install the MSXML Package.
Second open GMAX and export your model into the (Flightsim Aircraft Object (.MDL)).
At least import the exported ".MDL" model into “Modelxconverter” and export it at any format you needed (for example in the “*.3ds” format).
Import the “*3.ds” exported model into Blender and enjoy.