This document is the joint product of two industry committees: the EUROCAE Working Group WG-72, titled "Aeronautical Information Systems Security" and the RTCA Special Committee SC-216, also titled "Aeronautical Information Systems Security". WG-72 was formed to address information security for the overall Aeronautical Information System Security (AISS) of airborne systems with related ground systems and environment, while SC-216 was formed more specifically to address information security for certification of aircraft and its systems. Both committees agreed that the guidance provided by this document and its companion documents constitute aviation best practices to address the increasing potential for Intentional Unauthorized Electronic Interaction (IUEI) with aeronautical information systems. Both committees agree that the guidance is suitable for use as acceptable means of compliance in relevant jurisdictions. For a discussion of the usage of ED-201A/DO-391 and its relation with other EUROCAE/RTCA documents please see Appendix G. Appendix H provides a revision guide of the major changes to the ED-201 document, which was a sole publication of EUROCAE.