Unruly passenger incidents that threaten flight safety and security in the civil aviation sector have been increasing in recent years and bring many negative consequences for the sector. In this context, the purpose of this study conducted in the light of literature review, is to examine the causes of unruly passenger incidents in the civil aviation sector with a qualitative research. The phenomenological research method, one of the qualitative research designs, was used in the research. The sample of the research consists of 203 unruly passenger incidents that occurred between 2005-2020 and included passengers living in different geographical regions of the world. Document analysis method was used to collect data. The data obtained were subjected to content analysis with an inductive and descriptive approach using NVivo 12 program. As a result of the content analysis, seven themes that cause unruly passenger behavior were found. These themes are classified as reasons related to passengers, physical environment inside the aircraft, social environment inside the aircraft, failure to comply with the rules, airline service quality, reasons related to the airport and seasonal reasons. It is thought that the research will make an original contribution to the literature on the concept of unruly passenger and aviation security.