Advancing the state of aviation safety is a central mission of the National Aeronautics and Space Administration (NASA). Congress requested this review of NASA's aviation safety-related research programs, seeking an assessment of whether the programs have well-defined, prioritized, and appropriate research objectives; whether resources have been allocated appropriately among these objectives; whether the programs are well coordinated with the safety research programs of the Federal Aviation Administration; and whether suitable mechanisms are in place for transitioning the research results into operational technologies and procedures and certification activities in a timely manner. Advancing Aeronautical Safety contains findings and recommendations with respect to each of the main aspects of the review sought by Congress. These findings indicate that NASA's aeronautics research enterprise has made, and continues to make, valuable contributions to aviation system safety but it is falling short and needs improvement in some key respects.