You can get 2D files directly off the manufacturer’s websites, for large airliners anyway. The 3D data is of course proprietary and not just handed out to anyone, so anything you find will have been made by someone working off those drawings–which are often not very precise–and photos. They’re usually not very good. Unless it was stolen of course, which is not a great option.
If you know someone who knows someone who knows a subcontractor with sloppy policies, you might be able to get your hands on some ‘official’ 3D, but what you usually get is a model made by the graphics department that is pretty good but may not in fact be 100% correct either because it was purpose-made for rendering. Why? Well for an animation I was once given the real production assembly of a first-class seat. The part count was into 5 figures, it took solid days of work just to ‘dumb it down’ enough to be practical to render. And that was just a seat.