Which of the following factors can significantly affect the aircraft's CG?

The center of gravity (CG) of an aircraft is crucial for ensuring stability and proper handling during flight. One of the primary factors that can significantly affect the aircraft's CG is the fuel burn-off process. As an aircraft consumes fuel during flight, the weight of the fuel decreases, leading to a shift in the location of the CG. This shift occurs because the fuel is typically stored in tanks that are located toward the wings, and as the fuel is depleted, the overall weight reduces, and the CG may move rearward.

Understanding how fuel burn-off affects CG is vital for pilots because an incorrectly balanced aircraft can lead to poor performance and safety issues. Maintaining an appropriate CG is essential for optimal flight characteristics and ensuring that the aircraft responds predictably during maneuvers.

While other factors listed, such as weather conditions, time of day, and duration of the flight, can influence various aspects of flying, they do not directly affect the physical location of the center of gravity in the same manner that fuel consumption does. For example, weather may affect flight conditions and required performance but does not change the weight distribution within the aircraft itself.