This standard provides: a. interoperability requirements for the B2 ATN ground system to provide FANS 1/A aircraft with B2 data link services@ as defined by the B2 SPR Standard [4]. See 1.2.1. b. interoperability requirements to ensure seamless transition of ATS communications for bilingual aircraft (i.e.@ aircraft equipped with FANS 1/A and ATN data link technologies transitions from a FANS 1/A ground system to a B2 ATN ground system and vice versa). See 1.2.2. Purpose This document provides the interoperability requirements for an aeronautical telecommunication network for Baseline 2 ATS data communication services (B2) ground system that provides B2 air traffic data link services to future air navigation system 1/A (FANS 1/A) aircraft in oceanic and continental airspaces. Note: Based on ED-78A/DO-264 [1]@ INTEROP and SPR standards provide recommendations intended for government organizations@ conference of governments@ or agencies having statutory jurisdiction over the use and provision of air traffic services supported by data communications. These recommendations are for use by such government organizations to enunciate official policy@ related to such matters@ in aeronautical information publications (AIPs)@ notices to airmen (NOTAMs)@ airplane flight manuals (AFMs)@ and operator specifications.