If COTS products are used, the overall system security has to be watched carefully: when technologies are public and their specifications and developments are out of control of the aeronautical community, new discovered vulnerabilities and
threats using these products have to be followed and repaired as soon as possible. Also, Quality of Service (QoS) requirements, constricted bandwidth of the air to ground link, and weather conditions (which impacts the transmission quality) impose the reduction of additional overheads: any “static” security policy will be expensive in this case.