Aircraft targets in remote sensing images often have characteristics of similar shapes， especially the only slight differences between specific models， so that accurately detecting and recognizing fine-grained aircraft targets remains a challenge. Among current deep learning-based object detection methods， various improvements targeting different components of models can enhance detection accuracy between fine-grained categories to some extent. However， existing approaches overlook the importance of multi-scale discriminative features and inter-class separation constraints in fine-grained tasks， potentially limiting model performance from feature representation to feature discrimination. To address this issue， this paper proposes a Hierarchical and Orthogonal Fine-Grained Detection Network. The model effectively fuses multi-scale features from different levels using a gated fusion mechanism， enhances the representation capability of discriminative features under attention mechanisms with diverse receptive fields， and incorporates adaptive loss term weighting within the orthogonal loss function to strengthen intra-class compactness and inter-class separability of features. Consequently， the model’s capability for representing and discriminating fine-grained target features is improved. Comprehensive ablation studies and comparative experiments were conducted on two remote sensing fine-grained object detection datasets： MAR20 and SMID. Experimental results demonstrate that the proposed model achieves a mean average precision of up to 61.45% on the MAR20 dataset， representing an improvement of at least 0.43% and up to 6.29% over the baseline model and a mean average precision of up to 63.9% on the SMID dataset， surpassing the baseline model by a minimum of 1.7%. Across both datasets， the proposed model achieves the highest accuracy and performance compared to other mainstream algorithms.