TO provide increased ATC capacity to meet the 50% and 70% increase in air transport movements forecast by 2005, considerable attention is being focussed on automatic data exchange between aircraft and ground facilities. For various reasons the development of standards and procedures of the necessary integrity and the planning of implementation will take some years to complete, although the basic technology has been in existence for an appreciable time. The success of ACARS (aircraft communications addressing and reporting system) in improving airline operating efficiency over the years is well known.