Efficient airport ground handling operations are critical to ensuring timely aircraft handling and maintaining overall airport performance. These operations face tight schedules, resource constraints, and disturbances that can cause delays. Multi-skilled resources enhance flexibility by enabling multiple operations, reducing idle time and improving resilience to disturbances. Tactical optimisation of ground handling operations is investigated, focusing on allocating and scheduling multi-skilled resources. A new optimisation model is proposed to tackle the problem of allocating multi-skilled resources to interdependent ground handling operations under temporal, spatial, and disturbance-related constraints. To address the computational challenges of solving real-world problem instances, a heuristic-based approach is developed, as these instances prove too complex for traditional linear optimisation methods. The proposed approach is tested using a case study based on a full day of operations at Düsseldorf Airport, applied to a simplified layout representation, showing its ability to minimise delays and improve workforce efficiency. The results show significant advantages of incorporating multi-skilled resources, including increased flexibility and reduced delays. For example, with 600 resources and 60% disturbed operations, the higher-skilled resource set reduced total delay by 26% compared with the lower-skilled set. The heuristic solved all tested instances in less than one second, whereas exact optimisation required up to 24,097 s and became intractable for larger instances. These findings demonstrate that tactical scheduling with multi-skilled resources can improve both operational resilience and computational tractability. The results further show that the proposed approach extends existing ground handling planning methods by enabling proactive tactical scheduling under realistic operational constraints.