Gravity force is simply the weight of the flying system. Gravity forces are proportional to the amount of material needed to construct an object. The more materials and heavier those materials, the more a flying system will weigh. Drag and lift force result from the flow of air over the object. Lifting force induced by air flow over arched wing section.
Aerodynamic lift is the force that enables aircraft to stay in the air.
It is possible due to several principles of physics. When air moves over an arched surface, the air pressure above the surface drops. Wings on aircraft generally have an arched cross-section shape which causes air to speed up as it flows over the upper surface. As the air speeds up, the air pressure drops above the wing. The difference in air pressure between the upper and lower surface produces a force in the direction of low pressure.