The proliferation of precision-guided munitions (PGMs) poses a critical threat to NATO airbases, where concentrated high-value assets are vulnerable to saturation missile strikes. While active defences such as the Patriot system can intercept a portion of incoming threats, their finite capacity and unfavourable cost-exchange ratios underscore the need for complementary passive measures. This study employs a probabilistic, Monte Carlo–based simulation to quantify the protective value of Hardened Aircraft Shelters (HAS) under high-intensity attack conditions. Using Ämari Air Base, Estonia, as a representative NATO installation, the model integrates missile targeting logic, blast damage physics, active defence interception probabilities, and HAS degradation mechanics across 10,000 attack iterations. Two configurations are compared: the current shelter allocation versus an enhanced posture with additional HAS-protected aircraft. Results indicate that increased HAS utilisation reduces average aircraft losses by 4.6%, lowers exposed-to-sheltered loss ratios from 1.85:1 to 1.54:1, and decreases high-value asset kill probabilities by ~7%. While gains exhibit diminishing returns, HAS density also distributes targeting probability, indirectly enhancing survivability across the base. The findings affirm the continued relevance of Cold War-era hardening strategies in modern threat environments and support integrated, layered defence concepts combining active interception, sheltering, and deception to maximise operational resilience under saturation strike conditions.