The FAA, an agency of the Department of Transportation, is primarily responsible for the advancement, safety, and regulation of civil aviation, as well as overseeing the development of the air traffic control system. Its stated mission is to provide the safest, most efficient aerospace system in the world. This system, known as the National Airspace System (NAS), includes air traffic control systems, ATC procedures, operational facilities, aircraft, and the people who certify, operate, and maintain them. According to FAA, the system includes more than 19,000 airports, nearly 600 air traffic control facilities, and approximately 65,000 other facilities, including radar, communications nodes, ground-based navigation aids, computer displays, and radios, intended to provide safe and efficient flight services for the public. Over 46,000 FAA personnel and approximately 608,000 pilots operate about 228,000 aircraft within the NAS, including up to 2,850 flights at any given moment. The system operates on a continuous basis, 24 hours a day, every day of the year. As aircraft move across the NAS, controllers at several types of air traffic control facilities manage their movements during each phase of flight. According to FAA, these facilities include the following: More than 500 air traffic control towers supervise flights within about 5 miles from the airport runway. They give pilots taxiing and take off instructions, air traffic clearance, and provide separation between landing and departing aircraft. One hundred sixty Terminal Radar Approach Control facilities provide air traffic control services for airspace that is located within approximately 40 miles of an airport and generally up to 10,000 feet above the airport. These facilities handle sequencing and separation of aircraft as they approach major metropolitan areas. Twenty-two Air Route Traffic Control Centers (ARTCC) control and monitor airplanes over the continental United States and between airports. Controlling traffic usually at or above 17,000 feet, the typical center has responsibility for more than 100,000 square miles of airspace generally extending over a number of states. Three of the centers also control air traffic over the oceans. Controllers at these facilities work with pilots to ensure the flight path is smooth and free of other traffic. The Air Traffic Control System Command Center manages the flow of air traffic within the United States. This facility regulates air traffic when weather, equipment, runway closures, or other conditions place stress on the national airspace system. In these instances, traffic management specialists at the command center take action to modify traffic demands in order to keep traffic within system capacity. Figure 1 provides a visual summary of air traffic control across the different phases of flight. The FAA’s ability to fulfill its mission depends on the adequacy and reliability of its air traffic control systems, a vast network of computer hardware, software, and communications equipment. The agency relies on more than 100 air traffic control systems to process and track flights around the world. These complex and highly automated systems process a wide range of information, including radar, weather, flight plans, surveillance, navigation/landing guidance, traffic management, air-to- ground communication, voice, network management, and other information—such as airspace restrictions—that is required to support the agency’s mission. In order to successfully carry out air traffic control operations, it is essential that these systems interoperate, functioning both within and across facilities as one integrated system of systems. According to FAA data available at the time of our review, about one-third of air traffic control systems rely on Internet Protocol (IP)-based networking technologies for communication. FAA’s ongoing effort to modernize the ATC system is referred to as the Next Generation Air Transportation System (NextGen). NextGen involves changes to many aspects of air transportation, including the acquisition of new integrated systems (both software and hardware), flight procedures, aircraft performance capabilities, and supporting infrastructure to transform the current air transportation system into one that uses satellite- based surveillance and navigation operations instead of ground-based radar. These changes are intended to increase the efficiency and capacity of the air transportation system while maintaining safety and accommodating anticipated future growth. As demand for the nation’s increasingly congested airspace continues to grow, NextGen improvements are intended to enable the FAA to guide and track aircraft more precisely on more direct routes, reduce delays, save fuel, and reduce aircraft exhaust emissions. The following five key air traffic control systems perform critical air traffic control functions: FAA Telecommunications Infrastructure (FTI) forms the basic telecommunications infrastructure for NextGen, replacing the agency’s legacy networks to provide consolidated telecom services for the NAS. The FTI is also intended to reduce costs, improve bandwidth, and offer improved information security services, such as encryption, so that an enterprise-wide approach to information security assurance can be achieved. Surveillance and Broadcast Service System (SBSS) provides surveillance services to FAA and the aviation community. Most notably, SBSS provides the Automatic Dependent Surveillance- Broadcast service—one of the six NextGen transformational programs—which is FAA’s satellite-based successor to radar. This service makes use of Global Positioning System technology to determine and share precise aircraft location information, and streams additional flight information to the cockpits of properly equipped aircraft. En Route Automation Modernization (ERAM) replaces the legacy en route Host computer and backup system, developed more than 40 years ago. According to FAA, much of the system has already been deployed. ERAM is designed to be at the heart of NextGen and is key to advancing FAA’s transition from a ground-based system of air traffic control to a satellite-based system of air traffic management. As ERAM evolves, it is intended to provide benefits for users and the flying public by increasing air traffic flow and improving automated navigation and conflict detection services, both of which are vital to meeting future demand and preventing gridlock and delays. En Route Communications Gateway (ECG) is a communications system that receives data from sources outside the ARTCC, such as flight plan information and weather data, and passes it to other systems, including ERAM. Traffic Flow Management-Infrastructure (TFM-I) provides information processing support for FAA traffic management personnel as they coordinate the use of the NAS and respond to conditions of excess demand. TFM-I receives information on planned and active flights, generates forecasts of demand up to several hours ahead, presents this information to Traffic Management Personnel, and provides automation support for traffic management initiatives to resolve or ameliorate congestion. Each of these systems, in conjunction with many others that make up the NAS computing infrastructure, works to ensure safe flight passageways for aircraft in U.S. airspace from takeoff to landing. Safeguarding federal computer systems and the systems supporting the nation’s critical infrastructures, including the NAS, is essential to protecting national and economic security, and public health and safety. For government organizations information security is also a key element in maintaining the public trust. Inadequately protected systems may be vulnerable to insider threats as well as the risk of intrusion by individuals or groups with malicious intent who could use their illegitimate access to obtain sensitive information, disrupt operations, or launch attacks against other computer systems and networks. Accordingly, since 1997, we have designated information security as a government-wide high-risk area. In 2003, we expanded this high-risk area to include protecting systems supporting our nation’s critical infrastructure.those of agency inspectors general, describe persistent information security weaknesses that place a variety of federal operations at risk of disruption, fraud, and inappropriate disclosure. Our previous reports, and Recent federal guidance demonstrates that securing critical infrastructures from internal and external threats is a national priority. For example, in February 2013, the President signed Executive Order 13636, “Improving Critical Infrastructure Cybersecurity,” to address concerns about better securing critical infrastructure from cyber threats. This order, among other things, directed executive branch agencies to promote the adoption of cybersecurity practices; increase the volume, timeliness and quality of cyber threat information sharing; incorporate privacy and civil liberties protections into every initiative to secure critical infrastructure; and explore the use of existing regulation to promote cybersecurity. The order also directed the National Institute of Standards and Technology (NIST) to develop a technology-neutral voluntary framework for improving critical infrastructure cybersecurity. The framework, issued in February 2014, with business requirements, risk tolerances, and resources. is designed to help organizations align their cybersecurity activities Although many legacy air traffic control systems continue to rely on point- to-point communications, NAS systems, including NextGen systems, increasingly use IP technologies to communicate over interconnected computer networks. With the increased use of such technologies, however, comes increased risk: integrating critical infrastructure systems with information technology networks provides significantly less isolation from the outside world than predecessor systems, creating a greater need to secure these systems from remote, external threats. NIST, Framework for Improving Critical Infrastructure Cybersecurity, Version 1.0 (Gaithersburg, Md. : Feb. 12, 2014). The operational arm of the FAA is the Air Traffic Organization (ATO), which is responsible for providing safe and efficient air navigation services to the nation’s airspace. ATO is led by a Chief Operating Officer who reports directly to the FAA Administrator. The ATO includes seven service units: Air Traffic, Management, Mission Support, Program Management Organization, Safety and Technical Training, Systems Operations, and Technical Operations. Several entities within ATO share responsibility for information security- related activities over air traffic control systems. The NAS Security Risk Executive is the individual with overall responsibility for overseeing all information security-related activities across ATO, including the security of air traffic control systems. ATO’s Information Security Systems Group, within Technical Operations Services, includes NAS Cyber Operations (NCO), ISS Engineering, and an Authorization Team.