Description / Abstract: Presents the requirements for Two-Way Data Link Communication (TWDL) services. TWDL services include predeparture clearance, clearances, reports, and requests. In addition to testing standards, the document includes functional, performance, interface, and equipment standards for “ATCCOMM.” The term “ATCCOMM” as used in this document includes all components and units, including software, necessary for the aircraft equipment to support TWDL services with an ATC ground system peer via the Aeronautical Telecommunications Network (ATN).