In today's aviation alternative jet fuels play an increasingly important role. Their application incurs new engineering and environmental protection challenges. The key properties of their feasibility of integration are from technological point of view aging behavior and applicability as well as from environmental protection point of view the carbon footprint. During the comparison process experts can evaluate the above characteristics with linguistic variables. The application of linguistic variables always results in some degree of uncertainty – by their subjectivities. Fuzzy calculation methods are used to mathematically describe these uncertainties. The purpose of this study as a pilot project is to gain experience in developing a methodology of a multi-level fuzzy rule-based jet fuel qualification process.