RFID (Radio Frequency Identification) technology is widely used in science and technology, as well as in people's everyday life. To increase the range and access to hard-to-reach places, RFID technology can be used together with UAVs. The key parameters for the successful use of RFID on UAVs are the time and probability of successful tag reading. This work is devoted to assessing the time of tag reading from a reader attached to an unmanned aerial vehicle. For this purpose, various tag states are studied, as well as the time and probability of transition from one state to another. The paper proposes analytical and simulation models, as well as a comparison of the results obtained by these methods.