XPLMDestroyInstance
XPLM_API void XPLMDestroyInstance(
XPLMInstanceRef instance);
XPLMDestroyInstance destroys and deallocates your instance; once called, you are still responsible for releasing the OBJ ref.
Tip: you can release your OBJ ref after you call XPLMCreateInstance as long as you never use it again; the instance will maintain its own reference to the OBJ and the object OBJ be deallocated when the instance is destroyed.