The scientific principle that explains how airplanes generate lift is called Bernoulli's principle. According to this principle, an increase in the velocity of a fluid results in a decrease in its pressure. Airplanewings (or airfoils) are designed to create faster airflow over the top surface than the underside. This differential airspeed leads to lower pressure above the wing and higher pressure below, producing an upward force known as lift. The combination of lift, thrust, drag, and weight determines the overall flight dynamics of an aircraft.