Up-to-date information and communication technologies (ICT) implementation in various industries, on the one hand, increases the efficiency of different business processes and, on the other hand, generates new threats and vulnerabilities in ICT. Critical infrastructures (CI) need principal new effective methods and means for cybersecurity ensuring. In the situation with limited resources, CI objects defining and ranking is an important task. To rank objectively, CI objects should be assessed using some criteria. Previously, authors have proposed an FMECA-based method to assess importance level for state critical information infrastructure, which allows ranking and evaluating the importance of CI objects using both quantitative and qualitative parameters. This paper presents a complex experimental study of the proposed method using the aviation industry as an example. An experimental technique was introduced and using it, the adequacy of method response to changing input data was checked. It confirmed the possibility of importance level assessment of critical aviation information systems related to various categories: information systems for air navigation services; on-board information systems for aircraft; information systems for airlines and airports.