I collectively refer to "Multiplayer Clients" in case of plugins using the TCAS or multiplayer feature and dataRefs, which X-Plane offers as a standard way of displaying additional aircraft beyond the user's plane. Popular examples are XSquawkBox, X-IvAp, Swift, World Traffic, xPilot, PilotEdge...and certainly LiveTraffic itself. Last but not least, X-Plane's native "AI Aircraft" are the original. All of them draw planes into the sky.