There are four major forces acting on an aircraft in flight. Lift is the upward force allowing the aircraft to fly. Lift counters the weight that is holding the aircraft down. Thrust is the push or pull forward that allows the aircraft to move. Drag is a slowing force.
Drag always acts in a direction opposite thrust.
When air flows over the curved upper surface of a wing, it increases in velocity. This increase reduces the pressure above the wing and produces the upward force of lift. Lift Lift is the key aerodynamic force. During flight, pressures on the upper and lower surfaces of the wing are not the same. Although several factors contribute to this difference, the shape of the wing is the principal one.