Due to complex nature of aircraft heavy maintenance checks, achieving process stability is difficult. Literature suggests that this stability can be obtained by separating routine and non-routine work, and focusing on quick identification of non-routine tasks by completing inspection tasks early in the check. Current task planning methods show limitations in producing a feasible task planning, motivating the need for an advanced task planning model. This model combines the task elements of manpower, work order, and aircraft zone to find the minimum TAT given the task complexity-based heuristic. For this model, aircraft zones have been redefined, as the zones specified by Boeing are not suitable for task planning. An experiment using the advanced task planning model is conducted for the Inspection Phase tasks of the Boeing 777 C07 check. The target is to complete all tasks in 48 hours. Results show that it is feasible to perform all Inspection Phase tasks in 61.28 hours, where 99.51% of the tasks is completed in 48 hours. Completing all tasks takes 8 shifts, with a maximum of 31 technicians in a shift. The total TAT can be further reduced by identifying and lifting the constraints in the planning. One example shows how this can lead to an 8 hour reduction in total TAT for the best experiment scenario, bringing the TAT closer to the 48-hour goal. This demonstrates how the advanced task planning method can be used to stabilise aircraft heavy maintenance.