The advancement of ICT (Information and Communication Technology) is driving the development of various industrial technologies, as well as services in communication, transportation, logistics, and aviation. Urban Air Mobility (UAM) is expected not only to alleviate traffic congestion caused by ground traffic but also to provide rapid air cargo and passenger transportation services. Unlike general aviation services, Urban Air Mobility is intended for low-altitude flight operations. To provide seamless communication and reduce the impact of shadow areas, UAM can utilize existing commercial mobile communication base stations, leveraging the mobile communication network to achieve cost-effective infrastructure deployment. However, UAM is exposed to potential threats such as flight interference, obstruction from the ground, cyber threats including exposure, interception, and falsification of aviation information. The current UAM operating system's components (aircraft, pilots, control systems, vertiports, etc.) are vulnerable to unauthorized or illicit use, revealing weaknesses in the safe operation of urban air mobility systems. The operation of UAM using unauthorized objects poses potential threats like flight interference, obstruction, interception, falsification, and hijacking of aviation-related information (CSNi) from the ground. The reality is that the lack of mutual authentication among the components of the current UAM operating system—aircraft, control systems (ATC), vertiports, and their respective operators—exposes vulnerabilities to unauthorized use and security breaches. Therefore, this paper proposes an authentication structure capable of responding to potential cyber threats by enhancing the authenticity and security of the system through mutual authentication based on Public Key Infrastructure (PKI). This approach aims to prevent unauthorized use and control access to objects, thereby increasing resilience against replay attacks and other security threats.