The airborne collision avoidance system (ACAS) provides resolution advisories (RAs)
to pilots in order to avoid collisions. Controllers rely on pilots to report RAs by radio
as they occur in accordance with ICAO regulations. However these reports can come
late, incomplete or are absent in some instances. This solution consists of a set of
monitoring stations and a server system, which enable the continuous monitoring
and analysis of ACAS RAs and coordination messages between airborne units from
the ground.