Final answer:
A stall in an unmanned airplane's wing occurs when there is a disruption of smooth airflow and a degeneration of lift. This can cause the airplane to lose its ability to stay airborne.
Step-by-step explanation:
A stall in an unmanned airplane's wing occurs when there is a disruption of smooth airflow and a degeneration of lift. Both of these factors contribute to causing a stall. When the flow of air over the wing becomes turbulent, it disrupts the smooth flow of air and reduces the lift generated by the wing. As a result, the airplane loses its ability to stay airborne.