What defines the vertical axis of an aircraft?

The vertical axis of an aircraft is defined as the line that runs from the top of the aircraft to the bottom. This axis is essential for understanding aircraft movements, especially in relation to roll, pitch, and yaw. It represents how the aircraft may tilt or rotate vertically, influencing lift and descent. The vertical axis intersects with the other two principal axes: the longitudinal axis, which runs from the front to the back of the aircraft, and the lateral axis, which extends from wingtip to wingtip. This relationship among the axes helps pilots maneuver the aircraft effectively, allowing for coordinated flight operations.