Airplanes fly due to four main aerodynamic forces: thrust, which propels the plane forward and overcomes drag; lift, which is generated by the wings and counteracts the downward force of weight. In straight and level flight, thrust equals drag and lift equals weight. The wings generate lift through faster air flow over the top surface, creating lower pressure that effectively "sucks" the plane upward. Additional control surfaces like the horizontal and vertical stabilizers, rudder, ailerons and elevators help control the plane's movement.