During a flight, the pressure is lower on top of the wing than it is under the wing. The air tends to move from the high pressure below the wing to the low pressure above the wing around the wingtips. In the past, wingtips were straight, and the airflow caused severe turbulence.
So scientists decided to bend the wingtips upward to reduce turbulence, prolong the wings’ durability, and save a lot of fuel during travel. Thanks to this feature, we feel more comfortable during a flight.