What effect does "ground effect" have on an aircraft during takeoff and landing?

Ground effect refers to the increased lift and reduced drag experienced by an aircraft when it is flying close to a surface, such as the ground. This phenomenon occurs because the presence of the ground alters the airflow patterns around the aircraft. When an aircraft is in close proximity to the ground, the airflow is compressed, which generates additional lift. This can be especially beneficial during takeoff and landing phases, as it allows the aircraft to take off more quickly and reduces the amount of runway needed for landing.

As the aircraft reaches an altitude where ground effect is no longer significant, the lift provided by this phenomenon diminishes. Consequently, pilots must be aware of the impact of ground effect, particularly during landings, to avoid potential issues such as floating above the runway or improper touchdown.

In the context of the other choices, while drag can be affected by various factors, ground effect specifically increases lift and decreases drag at low altitudes, particularly during takeoff and landing, making the third statement the valid one.