What must be maintained in unpaved areas for air carrier use?

Turf and gravel surfaces must be maintained in unpaved areas for air carrier use to ensure that the operational environment is safe and usable for aircraft movements. These surfaces provide a stable and resilient foundation that supports the weight of aircraft while also allowing for adequate drainage to prevent water accumulation, which could lead to unsafe conditions. Proper maintenance of unpaved surfaces is critical for ensuring that they can withstand the stresses of aircraft operations and contribute to overall safety and operational efficiency at the airport.

Other elements such as runway markings or safety zones have their own importance but don't specifically pertain to the structural integrity required in unpaved areas. Drainage systems, while essential for managing water runoff, do not directly relate to the maintenance of the surface itself like turf and gravel do. Therefore, the focus on maintaining turf and gravel ensures that the specific needs related to surface quality and stability are prioritized for safe air carrier operations.