Can you please provide more detailed install instructions instead of just telling people they didn't install it correctly? I've done everything I can think of to get it to work. I just redid everything to be able to list out that I did basically everything possible even though I knew some of the things were completely wrong.
When I download the newest version of the mod, it comes as AirplanePlus_26.1.zip. If I put that into my KSP folder, it does nothing. If I put that into my KSP\GameData folder, it does nothing.
Now, let's extract the zip to get an uncompressed AirplanePlus_26.1 folder. Placing this in the KSP folder yields nothing. If I move the internal folders/file (AirplanePlus and Firespitter folders and ModuleManager.4.0.2.dll) outside of the AirplanePlus_26.1 folder but leave it in the KSP folder, nothing happens.
If I place the whole folder into my KSP/GameData folder, then I get some parts but I am missing many of them. Furthermore, there are no engine sounds -- even for stock parts. The same thing happens if I take the contents of the folder out and place them directly into the KSP/GameData folder.
In your instructions you mention that we need to place the GameData folder into the root folder. I can only assume that the root folder is the KSP folder. And when I extract the zip, there is no GameData folder. I do already have a GameData folder in my KSP folder. I tried everything I can think of based off of your instructions. I am able to get other mods to work perfectly fine, so I am struggling to understand why there is an issue with this mod.