Recently, the interest in Areal Unmanned Vehicles (UAVs) has significantly increased which is mainly due to their important and appealing applications including disaster detection and management. UAVs are usually equipped with antennas in order to send or receive data wirelessly. Efficient antennas are essential for robust and continuous communication between the UAV and other devices across various operational scenarios. Different antennas have been already proposed for UAVs. However, they have a number of limitations and shortcomings and hence additional efforts are required to obtain more efficient and better-performing designs. In this paper, antennas used in UAVs are reviewed. Challenges and requirements for the antenna design and performance are outlined. Moreover, popular antenna types are surveyed with a focus on highlighting their existing shortcomings and exploring potential future directions. This paper also sheds light on the specific requirements necessary for antennas in early warning systems which have not been frequently discussed in literature.