Starting with X-Plane 11, all aircraft must be installed in a folder within "Aircraft".* We're taking this opportunity to normalize where Aircraft are installed (all other files have to go in 'the right' folder, e.g. Weapons, Airfoils, Custom Scenery, etc.). This will let us search a much smaller footprint of files to find installed aircraft, which speeds up the UI.
Our aircraft are in a folder called "Laminar Research" within Aircraft; my suggestion is that vendors (and a lot of you are already doing this) have your own folder in Aircraft where aircraft go.
The goal is to have a file structure where it is not necessary to reorganize where files live or deconflict, so that automatic updaters (ours and third parties) can find the files they installed. The old folders-with-categories-of-aircraft are now gone.
You can make any set of folders within Aircraft you want, and when you search in the UI, you can search by folder names. But we also provide a bunch of other ways to find aircraft, e.g. type, studio, number of engines, or file name search.
*If you thought X-Plane already required it, well...nope - X-Plane 10 will load an aircraft anywhere in the X-Plane folder. This is only true for Aircraft - everything else has to go in the right bucket.