When terrestrial communications partially or completely fail, rapidly deployable non-terrestrial overlays can be decisive to preserve essential services. This thesis presents a modular simulation framework for multi-HAPS (High-Altitude Platform Station) networks targeting urban environments and large-scale outages. The framework integrates realistic MU-MIMO air-interface modeling, antenna directivity, and weather-aware propagation losses (free-space, atmospheric gases, rain, cloud/fog) within a priority-aware management layer. The architecture extends to HAPS-to-HAPS operation, enabling cooperative overlays when terrestrial infrastructure is degraded or unavailable. Evaluation over Paris, using Orange mobile-traffic traces, compares user association, scheduling, and content placement under fair-weather and worst-day meteorology. A BestHAPS association balancing link quality, platform load, and backhaul headroom, combined with weighted proportional-fair scheduling delivers robust per-area beam capacity (averaging ≈ 100 Mb/s).