Carbon fiber-reinforced polymer (CFRP) composites are widely used in aircraft structures for weight reduction due to their high specific strength and modulus. However, their weak interlaminar properties lead to high sensitivity to out-of-plane loads such as impact, making them prone to delamination damage, which threatens flight safety. To enhance interlaminar performance, through-thickness reinforcement technologies, particularly Z-pinning and stitching, have become key research focuses. This paper systematically reviews the manufacturing processes, structural mechanical characteristics, and application progress in aerospace structures of these two mainstream through-thickness reinforcement technologies. Research shows that Z-pintechnology, by implanting metal or CFRP pins, and stitching technology, by sewing multiple fabric layers with fiber threads, both effectively bridge interlaminar cracks, significantly improving the impact resistance of composites. However, the implantation processes introduce defects such as fiber waviness, breakage, and “eye-shaped” resin-rich zones, leading to varying degrees of reduction in in-plane tensile, compressive, and shear properties. Key parameters, such as Z-pin diameter/density/insertion angle, stitch thread diameter/density/pattern, decisively influence the performance enhancement and trade-offs. At the application level, Z-pin technology is mature, suitable for localized toughening of prepreg laminates and joint reinforcement, and is easily integrated into existing processes. Stitching technology, combined with automation and resin infusion processes, demonstrates unique advantages in manufacturing large-scale integrated structures, significantly enhancing damage tolerance. Despite their significant potential, the application of through-the-thickness reinforcement technologies in primary aircraft load-bearing structures remains limited. Their long- term performance under hygrothermal environments and fatigue endurance require further validation. Future efforts should focus on optimizing parameters to balance performance trade-offs and exploring new directions such as integrating health monitoring.