The scientific principle that explains why planes fly is known as Bernoulli's principle, which is associated with the shapes of the wings (airfoils). As air flows over the curved upper surface of the wing, it moves faster than the air underneath, resulting in lower pressure above and higher pressure below. This pressure difference creates lift, allowing the airplane to rise into the air. In addition to Bernoulli's principle, thrust generated by the engines and the balance of lift and weight are critical for flight. These principles combined enable aircraft to take off, cruise, and land safely.