 The FAA implemented a prototype system around 2003 but did not manage to convince airlines to install VDL Mode 3 avionics and in 2004 abandoned its implementation.The ICAO standard for VDL Mode 4 specifies a protocol enabling aircraft to exchange data with ground stations and other aircraft.VDL Mode 4 uses a protocol (Self-organized Time Division Multiple Access, STDMA, invented by Swede Håkan Lans in 1988) that allows it to be self-organizing, meaning no master ground station is required.