What is one necessary action before weighing the aircraft?

Before weighing an aircraft, completing a pre-flight checklist is crucial. This checklist typically includes verification of essential parameters such as fuel levels, passenger counts, baggage weights, and any cargo that may affect the aircraft's overall weight. Ensuring that all systems are checked and that the aircraft is prepared for weighing allows for accurate calculations of weight and balance, which are critical for the aircraft's safe operation.

The other options do not contribute to the accuracy or safety of the weighing process. Ensuring the aircraft is in motion is irrelevant for weighing purposes, as the weight must be measured while the aircraft is stationary. Adjusting the passenger load may not be necessary unless there are miscalculations or last-minute changes, but it does not ensure the aircraft is ready to be weighed. Ignoring fluid measurements would lead to inaccuracies because fuel and other fluids are part of the total weight that must be accounted for. hence, completing the pre-flight checklist is the most comprehensive and necessary action to take before weighing the aircraft.