Flying Ad-hoc Network (FANET) [1] is a subclass of Mobile Ad Hoc Networks (MANETs). In FANET, a group of Unmanned Aerial Vehicles (UAVs) are communicating to execute a given task. They are connected through the wireless communication channel without any support of established infrastructure [2]. In FANET, UAVs can fly autonomously based on pre-programmed flight plans or can be operated using complex dynamic automation systems, and are versatile and flexible in implementation [3]. When ordinary communication infrastructure is out of service or simply not available, a group of small flying robots can provide a rapidly deployable and self-managed ad-hoc Wi-Fi network to connect and coordinate rescue teams on ground [4]. FANETs have a wide range of applications such as disaster management, location aware services, rescue operations, and security services. [5]. Similar to MANETs, FANET nodes are free to move in any direction to complete assigned task, due to which the network topology changes frequently. Nodes can join or leave the network as and when required. FANET is a subclass of MANETs that offer self-organized and independent behavior of nodes which may lead to malicious and selfish behavior of nodes in the network [3,6,7]. Due to heterogeneous applications of FANETs, it is mandatory for nodes to follow the protocols and cooperative behavior, highlighting the need of security of such networks. Classical methods of security, i.e., cryptographic techniques, demand more resource consumption [8]. Hence, securing FANETs with limited resources becomes an essential need to research. Past research has been done for trust management in the area of ad-hoc networks, indicating that trust management techniques are helpful in securing ad-hoc networks from various kinds of attacks [6]. Hence, in order to secure FANETs, the concept of trust management is viable [8]. Trust management systems maintain the trust relationships between participating nodes. This chapter focuses on various available trust computation methods for MANETs which can be adaptable for FANETs.