Three digital communications networks of the FAA performing essential services in support of the National Air Space System (NAS) are described and discussed. Designated as the Aeronautical Fixed Telecommunications Network (AFTN), the combined Weather Teletypewriter Networks A, C, and O, and the Service B Teletypewriter Network, respectively, these systems carry national and international digital message traffic in support of air traffic control operations and aeronautical weather services. These data are exchanged among the Air Traffic Control Centers, Airport Terminal Facilities, and Flight Service Stations of the FAA and in the case of weather data, with offices of the National Weather Service Military Weather and Flight Operations Offices, airlines, and other commercial and industrial interests. Recent and planned modernization programs resulting in the introduction of major computerized electronic message switching centers are also discussed. The electronic data processor configurations, their modes of operation, and specialized data handling features are described. Planned transition and progress to date in converting from 100 word/min teletypewriter operation to medium speed 1200-2400 Bd data rates and from manual inputs to the increasing use of computergenerated messages and computer-to-computer data exchanges are indicated. With the introduction of computerized switching and control centers the overall integration of FAA communications networks into a more fully unified total communications system with more standardized procedures and formats becomes more practical and achievable. Basic concepts and progress towards this goal are outlined.