I am not with Laminar Research, just a flight simmer.
In addition to the answer given by Cailean you may wish to have a look at the following site at https://forums.x-plane.org/index.php?/files/
A large portion of these items developed by other X-Plane flight simmers are freeware.
Also have a look at the on-line XP11 manual found at http://x-plane.com/manuals/desktop/ Scroll down in the opening pages for a list of supplied aircraft.
Hope this helps.