When migrating, geese always gather in groups of dozens, hundreds, or even thousands, flying in formation one after another. Ancient people called this formation the "goose formation". The goose formation is led by an experienced lead goose. When accelerating, the group forms a "V" shape. Once the speed slows down, the group changes from the "V" shape to a long, serpentine "I" shape, which is an effective measure for long-distance migration.
Aerodynamicists have found that during flight, the airflow pressure on the lower surface of an airplane's wing is greater than that on the upper surface. This pressure difference not only provides lift for the airplane, but also causes the airflow below the wingtip to deflect upward, forming two induced vortices. The induced vortices create an upward airflow on the outer side of the wing and a downward airflow on the inner side, resulting in induced drag on the airplane.
During flight, geese also generate similar induced vortices at the wingtip. When the geese fly in a "V" formation, all geese except the lead goose encounter the upward airflow generated by the induced vortices, thereby saving energy consumption during flight. Since the lead goose cannot enjoy this upward airflow and is the most tiring member of the flock, the geese take turns as the lead goose to ensure that all members can fly to their destination.