My document folder has a folder called Aerofly FS2 and it there is a folder called 'scenery'. However, there also is a folder called 'scenery' within the folder called 'addons'.
I just tried to install mesh and it didn't work when I placed it in 'scenery'. I had to place it in 'addons/scenery'.
However, I also installed textures and places and those did work when I placed them in 'scenery'...
So... when am I supposed to put things in 'scenery' and when in 'addons/scenery'...? It's a bit confusing.