The pressure in a moving fluid depends on the velocity of the fluid.
Bernoulli’s principle states that pressure is inversely proportional to the velocity of a flowing fluid.In a steady flow of fluid, the pressure in the liquid is low when velocity of the liquid is high. Similarly the pressure in the lquid is high when the velocity of the lquid is low.
The lift or upthrust that enables an aeroplane to fly is caused by the flow of air around its wings. The wings of an aeroplane are in the form of an aerofoil. Its top surface is curved while the bottom is flat. As the plane cuts through the air, The air has to travel faster over the top than the bottom of the wings. Hence the air pressure on the top of the wings is lower than the air pressure at the bottom of the wings. The difference in air pressure on the top and bottom of the wings produces an upward force or lift that pushes the wings upwards.