Question: must have addons for fsx?
Answer: FSX users. SimConnect (FSX:SE users only) – free. ... 
Prepar3d users. FSUIPC (all users) – free.
Read more. Read more about the first steps in upgrading your FSX. ... 
Weather engine. ... 
Cloud and sky textures. ... 
Moon. ... 
FSX / P3D. ... 
Freeware ground textures.