What happens to drag when thrust is less than drag?

When thrust is less than drag, the aircraft experiences a situation where the aerodynamic forces acting against it (drag) exceed the force propelling it forward (thrust). This imbalance means that the aircraft is unable to maintain its current speed, leading it to slow down.

In this scenario, as the drag force continues to work against the aircraft's forward motion without sufficient thrust to counteract it, the result is a decrease in velocity. This principle is fundamental to understanding how the forces acting on an aircraft interact during flight. By recognizing that a deficit in thrust relative to drag leads to a reduction in speed, it becomes clear why this outcome is the correct choice.

Other scenarios, such as the aircraft speeding up, descending, or maintaining speed, would require either a balance of forces or a greater thrust to overcome the drag, which is not the case when thrust is less than drag.