Ask an Explainer

When looking at the wing of a flying airplane, air will move the fastest above a wing and the slowest below the wing. To see how the speed of air changes, we need to look at the wing of an airplane.  If we look at a wing, and slice it like bread slices, we will see the cross section or airfoil of the wing.  Air travels at different speeds above and below the wing because of its shape.  On top of the wing, there is less space for air to move, so it moves more quickly.  Another way to think of this is to imagine a garden hose.  Water flows quickly through a garden hose, and it moves even faster if your thumb covers part of the entrance.  All of that water is still trying to escape, but there is less room so it must move faster!  This is the essence of the Bernoulli Principle, which explains why air travels more quickly above the wing than below the wing when a plane is in flight.  To experiment with Bernoulli's Principle, try this Bernoulli Brain-Teaser!