system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do some airplanes have the wing tips folded up at about 80 degrees and some planes do not?
gpt
A wing provides lift because it creates low pressure on top of the wing, and higher pressure below. As a side effect this causes the air to swirl around the tip of the wing in an effort to equalize the pressure as air on the high pressure side tries to reach the low pressure side. This is undesirable because it screws up the airflow around the end of the wing, and also creates dangerous vortexes that trail behind the aircraft. One way of minimizing this problem is by using "winglets" that serve as a fence to block the air under the wing from being able to curl around the end. This makes the wing work more efficiently and reduces those vortexes.