The article is a continuation of the Author’s study on the ways to ensure the quality and safety of aeronautical data and information in the entire process of those data and information creation, collection, processing and publication. This time, however, the emphasis was placed on the possibility to use the DMAIC methodology for diagnostics of potential incompatibilities in aeronautical data request process. At the beginning the DMAIC methodology was presented and the aeronautical data and information, as well as the aeronautical data chain, were described. The Author paid special attention to the data request process, as it is considered to be the most critical chain’s stage. The proceeding diagram for this process, based on valid legal requirements, was elaborated and described. Then the concept of DMAIC methodology application was presented together with the proposed changes in the mentioned proceeding diagram. Finally, regarding the FMEA analysis, presented in one of the previous articles [19], the new values of FMEA rating scales for: consequence of failure - variable S, likelihood of failure - variable R and the most important one - the ability to the detect the problem - variable W were estimated. At the end, conclusions were drawn.