Explain · analogy · Serious version
How planes stay in the air in terms of a skimming stone
An aircraft stays airborne by using its wings to push air downwards, which generates an upward force known as lift that opposes the pull of gravity.
Think of an aeroplane wing as a very expensive, metal skimming stone that refuses to sink. As the engines propel the craft forward, the curved shape of the wings forces air to travel faster over the top than the bottom. This pressure difference is the flick of the wrist that keeps the stone skipping across the surface of a pond, provided the pilot keeps the speed high enough to stop the stone from losing its momentum and hitting the mud.
The air acts just like the water tension on a village pond in Surrey. If the stone stops spinning or loses velocity, the surface tension fails and gravity reclaims its property with a rather unceremonious splash. Wings maintain this altitude by constantly deflecting air molecules downward, a process that is essentially the aeronautical equivalent of skipping a flat piece of slate across the lake until you reach the far bank or run out of fuel.
Maintaining this state requires the pilot to balance thrust and drag, much like choosing the perfect angle to ensure your stone does not dive straight to the bottom of the lake. If the wing angle of attack is too steep, the stone stalls, the air flow detaches, and the flight path ends in a way that would be quite concerning for anyone holding a lukewarm latte in row twelve.
Where the analogy breaks downA stone eventually stops due to friction and gravity, whereas a plane requires continuous engine thrust to maintain the speed necessary for lift.