The aviation system is one of the principal users of weather information. Assessing the benefits of weather information to aviation is important in a number of contexts: 1. Detemining the priority of investments in aviation weather information vis a vis other options for transportation and/or weather system investments, 2. Determinins priorities for research, implementation, facility staffing and information distribution, 3. The allocation of roles and responsibilities between various government agencies and private industry for various functions, and 4. Use in forecasting to set thresholds (see, e.g., [Felton, 1991], [Andrews, 1993], and [Liljas and Murphy, 1994]) With reduced government funding in a variety of areas related to aviation weather and with cost pressures on the users of the weather information (especially the air carriers), the importance of carefully performed benefits assessment has increased significantly in the past decade and is expected to become even more important in the near future. Our discussion will focus on safety and delay reduction. In the case of safety, we will consider in some depth the case of the deloyment of wind shear detection systems, while delay reduction will focus on results from recent studies of improved information on airport weather. In each case, we will also identify issues related to other benefits assessments in these areas.