Modified airplanes and free modified add-ons/fixes are placed in the community folder. This may increase the load time when starting the sim. Since their creators vary, its contents will not update on their own.
I’m assuming you do not have any mods installed at this time so don’t worry about it.
More information on locating the folder:Community Folder Part X
You would move the contents anywhere else to see if that is the problem with loading. You can also get a community folder manager which creates and deletes shortcuts in the community folder (works the same as if the files are actually located there). That way you can enable only the mods you wish to use at that time. I personally haven’t experienced much increase in load time and have a few gigs worth of mods.