In a July 30, 2007 article in NWS Focus, acting Assistant Administrator for Weather Services Mary Glackin reiterated “the need to develop a better understanding of our customer requirements and our science and technology baseline” for aviation weather. Constraints on the aviation enterprise typically comprise phenomena which exist at the storm and micro scales. These constraining phenomena include thunderstorms, icing, turbulence, and volcanic ash. Emerging problems for the aviation enterprise are hazards caused by solar radiation (aka space weather) and atmospheric chemistry which also occur at these scales. Until recently, observing requirements for, and mission impacts associated with, these phenomena have not been comprehensively documented in a single, authoritative source. Scientists at NASA and NOAA have recently completed this task and have established baseline observational requirements for the Next Generation Air Transportation System (NextGen) and expanded and updated the NOAA Consolidated Observational Requirements List (CORL) for the NOAA Aviation Program to better plan investments for current and future observing systems. This paper describes the process and results of this effort. These comprehensive aviation observation requirements will now be used to conduct gap analyses for the aviation component of the U.S. Integrated Earth Observing System and to inform the investment strategies of the FAA, NASA, and NOAA that are needed to develop the observational architecture to support NextGen and for the reduction of the effects to the nation from high impact weather such as hurricanes and flash floods.