In XP, you can make a very basic shape and form of your aircraft. You set the flight parameters for how your aircraft will function. You have to use a 3D modeling program that can export to XP's own .obj format. Most devs use Blender or conversion programs from their 3D app to XP. Then you can build your 3D model and export it into XP. By making the XP's model invisible and adding your build, XP will use your build for looks and XP's build for function.