Deep learning model for multi-class 3D segmentation of the aorta and its thirteen branches from CT angiography, intended to support planning of endovascular aortic interventions. CIS-UNet combines a CNN encoder with a symmetric decoder and a novel Context-aware Shifted Window Self-Attention (CSW-SA) bottleneck block that adapts the Swin transformer's patch-merging mechanism to more efficiently capture global spatial context. Trained and evaluated via 4-fold cross-validation on the first public multi-branch aorta CTA dataset (59 patients), CIS-UNet outperformed the state-of-the-art SwinUNETR baseline, achieving a mean Dice of 0.713 vs. 0.697 and mean surface distance of 2.78mm vs. 3.39mm, while being more computationally efficient.