Air transport is a growing industry today, and passengers frequently prefer it because it is faster than other modes. As a result, there is an increasing demand for air transportation, not only in terms of passengers but also in terms of logistics, creating a competitive environment in the industry. Airline companies are willing to enhance their fleet to meet this thriving demand. Therefore, fleet planning and aircraft selection are crucial issues to be managed by airline firms. Fleet planning experts should analyze aircraft types under vagueness based on criteria to select the most appropriate one according to the company’s needs. This paper evaluates aircraft alternatives considering three main financial, technical, and environmental categories under fuzzy and vague conditions. This study helps high-level executives make appropriate decisions among alternatives by considering necessary conditions. The multi-criteria decision-making method, Analytic Hierarchical Process (AHP), uses inter-valued spherical fuzzy sets. The method is explained in detail, and the results are analyzed.