The degree of recognition of the efficiency of an airline plays an important role in the planning and future success of that company. However, a handful of studies have addressed the issue of factors affecting the efficiency of airline companies in Iran. It is obvious that the first step to measuring the efficiency of any organization is to know the factors affecting its efficiency, which ultimately leads to knowing the inputs and outputs. The aim of this study is to identify the appropriate inputs and outputs to measure the efficiency of Iran's airlines. These companies are organizations whose responsibility is to carry passengers and cargo. In this study, the Fuzzy Multi-Criteria Decision-Making approach (FMCDM) is used for this issue. First, by using the existing literatures, effective factors identified. Then by viewpoints of the experts having activities in the field of aviation, including pilots, engineers, and aviation experts, inputs and outputs indices are appropriately redefined. For this purpose, a questionnaire containing 12 questions as inputs and 7 questions as outputs was provided. During the 2 stages-screening, using the fuzzy Delphi method, finally, 6 input parameters in the 3 groups and 3 output parameters in the 2 groups were identified and extracted. The paired Comparison Analysis method is used for weighting input indices.