<p>Civil aviation continues to face evolving threats of unlawful interference, including terrorism, hijacking, sabotage, and cyber-enabled attacks. Although regulatory frameworks, technological capabilities, and international cooperation have strengthened considerably, evaluating the effectiveness of aviation security remains largely centered on procedural compliance and incident-based indicators. This study adopts a practice-oriented perspective by examining how aviation security effectiveness is interpreted and assessed by professionals directly involved in implementing security measures. Drawing on in-depth interviews with experienced aviation security and safety practitioners, professional narratives were analyzed thematically to explore how deterrence, vulnerability, and security effectiveness are understood in operational settings. Guided by deterrence theory, the analysis demonstrates that practitioners associate effective security not only with technological capability and regulatory compliance, but also with consistent implementation, professional judgment, organizational coordination, and alignment with international standards, particularly those established by the International Civil Aviation Organization (ICAO). Participants also identified persistent challenges associated with human factors, resource constraints, and evolving threat environments, while emphasizing insider threats as a context-dependent source of vulnerability requiring sustained organizational vigilance. Rather than offering broadly generalizable conclusions, the study provides context-specific insights into how deterrence is interpreted and enacted in contemporary aviation practice. In doing so, it complements predominantly technical and regulatory perspectives by highlighting the value of practitioner narratives for informing future research, operational decision-making, and policy discussions concerning aviation security.</p>