https://qz.com/1333190/scientists-have-invented-a-group-of-self-flying-drones-that-think-collectively/

European scientists have invented a group of drones that act autonomously, and in relation to each other. The 30 drones fly together without any human control or pre-programming.

Usually large groups of drones are programmed to follow a path, like the drone display at the 2018 Winter Olympics. These drones make decisions themselves using sensors and communicating with each other. They manage to stay within a designated area, separating in front of obstacles and coming back together.