GAO was asked to review FAA’s cybersecurity efforts. This report (1) identifies the cybersecurity challenges facing FAA as it shifts to the NextGen ATC system and how FAA has begun addressing those challenges, and (2) assesses the extent to which FAA and its contractors, in the acquisition of NextGen programs, have followed federal guidelines for incorporating cybersecurity controls. GAO reviewed FAA cybersecurity policies and procedures and federal guidelines, and interviewed FAA officials, aviation industry stakeholders, and 15 select cybersecurity experts based on their work and recommendations by other experts.