3D plane recovery from monocular images constitutes a fundamental task in indoor scene understanding. Recent methods formulate this problem as 2D pixel-level segmentation through convolutional networks or query-based architectures, which purely rely on 2D pixel features while neglecting the inherent 3D spatial nature of planar surfaces. To address this limitation, we propose an end-to-end Plane Reconstruction, Aggregation, and Splatting (PlaneRAS) framework that explicitly leverages 3D geometric reasoning combined with online planar primitive reconstruction. Our framework introduces two core components: 1) a reconstruction module utilizing customized planar primitives to compactly represent 3D scene, and 2) a recovery module that aggregates local primitives to derive globally consistent plane instances. The proposed 3D-aware representation enables direct integration of pretrained geometric priors, significantly enhancing performance beyond conventional 2D-centric approaches. Extensive experiments on ScanNet and NYUv2 datasets demonstrate state-of-the-art results across various evaluation metrics, resulting from our explicit 3D geometric modeling and effective fusion of cross-dimensional features.