Why it is possible for air passenger to get an electrical shock when he touches the knob of the toilet door in a high altitude flying airplane?

Passengers may experience an electrical shock from touching the toilet door knob in a high-altitude airplane due to static electricity buildup. As the aircraft moves through the atmosphere, friction between the air and the plane can generate static charges. When a passenger touches a conductive surface like the door knob, the static charge may discharge, resulting in a mild shock. This phenomenon is more likely to occur in dry air conditions, which are common at cruising altitudes.