Which item is included in an aircraft's basic empty weight?

The inclusion of unusable fuel in an aircraft's basic empty weight is based on the definition of this weight category. Basic empty weight refers to the weight of the aircraft with all essential components and fluids necessary for operation, excluding any payload. This includes the airframe, engines, operational equipment, as well as any fluids like oil and unusable fuel. Unusable fuel is specifically factored in because it represents fuel that cannot be utilized for flight purposes, thus affecting the overall weight the aircraft is carrying when it is ready for action.

Other elements such as passengers, flight crew, and payload are not included in the basic empty weight. The weight of these components falls under operational weight categories, which are considered separately when calculating how much the aircraft can carry or the load during a flight. Therefore, understanding the distinction helps in more accurately calculating aircraft performance metrics and adhering to safety guidelines.