During what condition is an aircraft's weight most accurately measured?

The most accurate measurement of an aircraft's weight occurs in a level flight attitude. When an aircraft is in level flight, the forces acting on it—specifically, the lift produced by the wings and the weight of the aircraft—are balanced. This condition allows for the most precise understanding of the aircraft's total weight because all dynamic factors that could influence weight readings, such as acceleration or deceleration, are neutralized.

When an aircraft is on the ground before fueling or loaded with passengers and cargo, external factors like ground surface conditions or fuel distribution can impact weight readings. In-flight measurements can be influenced by changes in environment, such as varying atmospheric pressures and the aircraft’s orientation during maneuvers. Therefore, while measuring weight in a level flight attitude provides the most stable and accurate reading, other conditions may introduce variables that affect the precision of weight measurement.