the next-generation wireless applications, including sensor applications (e.g., surveillance, personal, body, and environmental monitoring) and those based on holographic and haptic operations (e.g., virtual reality/VR or augmented reality/AR). Securing a UAV flying base station is critical because it is a part of the cellular service provider infrastructure and the mobile users rely on it for connectivity. Its disruption and manipulation represent high security risks, as our everyday lives increasingly depend on reliable connectivity. In addition, the advancements and developments in wireless/mobile implementations, including software-defined radio (SDR) and open-source mobile networking softwares such as srsRAN, reduce the threat implementation barrier and increase the attack feasibility (even though these enabler tools and technologies provide longer-term benefits in securing the system, including improving the transparency, vendor interoperability, and security awareness). We therefore treat the networking provider infrastructure as a critical infrastructure and focus on the integrity of flying base station operations (execution is as designed, and the unauthorized attackers cannot manipulate or change the protocol execution) and availability (the connectivity is provided when needed and requested). The UAV drone flying base station system combines a telecommunications base station (for its application and purpose of connectivity provision) and UAV drone (for mobility implementation and control). While there has been research and development to secure the component technologies of the flying base station system (communications for base station, embedded control for UAV drone, and distributed computing for the base station's coexistence with other base stations and the rest of the infrastructure), research and developments taking a systems approach to secure the flying base station as a system have been lacking. In this review paper, we therefore identify the unique properties of a flying base station distinct from its component technologies, review the related research in the component technologies (based on which we can draw the initial reference designs for the security solutions before adapting and advancing them for flying base station), and discuss future work directions. We envision that this paper will inform, encourage, and facilitate further research to advance the security of flying base stations. This review paper surveys the existing research literature on UAV flying base station security, identifies research gaps for the flying base station system built on its component technologies, and informs readers about future research directions. To the best of our knowledge, this is the first review paper focusing on the security of UAV flying base stations. [PERSON] et al. (2018) use UAV to enable physical-layer security but lack the systems approach, i.e., they do not consider the flying base station system aspects of UAV/drone control, battery, and digital security. Other survey or review papers focus on the individual component technology or lack a security focus, e.g., UAV/drone sensing and monitoring (e.g., ([PERSON] et al., 2018)), communications to enable UAV/drone operations (e.g., ([PERSON] et al., 2018; [PERSON] et al., 2018)), the security of UAV drones (e.g., ([PERSON] et al., 2018; [PERSON] et al., 2018; [PERSON] et al., 2018; [PERSON] et al., 2018)), security of wireless communications, and security of wireless and mobile applications (e.g., ([PERSON] et al., 2018; [PERSON] et al., 2018)). The rest of the paper is organized as follows. Section 2 describes the telecommunications networking background involving base stations focusing on the most recent 5G New Radio (NR) standardized protocol. Our treatment of the background information on telecommunications is brief and of a high level as we describe those factors needed for flying base station research as opposed to providing significantly longer and more detailed coverage of the 5G NR protocol.