What constitutes the 'useful load' of an aircraft?

The useful load of an aircraft refers to the total weight that can be carried by the aircraft aside from its own weight. It primarily includes the weight of passengers, baggage, and usable fuel, as these are the critical components that directly affect the aircraft's performance and operational capacity. This definition is key for pilots and operators who must understand the limitations imposed by weight for safe flight operations.

In the context of this understanding, the correct answer accurately captures the components that make up the useful load, as it specifically highlights passengers and usable fuel as the primary elements. In contrast, other options like fixed equipment or the weight of the aircraft itself do not pertain to the useful load and focus on different aspects of an aircraft’s weight and configuration. The distinction between the total weight and what constitutes useful load is essential for flight safety and operational planning.