The En Route Communications Gateway (ECG) is a mission-critical interface for surveillance and flight data. It provides the portal for the transfer of aircraft flight plan and surveillance data to other En Route systems – both legacy systems and critical Next Generation Air Transportation System (NextGen) technology, such as the En Route Automation Modernization (ERAM) program and Automatic Dependent Surveillance - Broadcast (ADS-B), while providing added network communications. The ECG system is modular in design, and system capacity can be incrementally increased as air transportation demands change.