adsbexchange.com collects data from volunteers, of which there are currently fewer than 500 around the world. One person can usually only pick up aircraft with

adsbexchange.com collects data from volunteers, of which there are currently fewer than 500 around the world. One person can usually only pick up aircraft within a hundred miles or so. Many "interesting" aircraft don't broadcast their position, so you won't see them on a map unless they can be triangulated (actually multilaterated)--but that requires that multiple nearby volunteers receive their signals. That's why you don't see a lot of aircraft on the map, not a failure of realism.