This paper proposes a technique for selecting the optimal transmission antenna in a UAV communication environment based on the Gated Recurrent Unit (GRU) model. The considered communication system employs multiple antennas and operates in a bidirectional communication mode through Time-Division Duplexing (TDD). In this system, all antennas receive signals, and the optimal transmission antenna is selected based on the Signal-to-Noise Ratio (SNR) of the past received signals for subsequent transmission. Existing methods for selecting the transmission antenna include the average method, which uses the average SNR of received signals, the recent value method, which uses the SNR of the most recently received signal, and a method based on CNN. The experimental results show that the proposed GRU-based approach outperforms the existing methods in terms of antenna selection accuracy in both wideband and narrowband scenarios.