Each drone cost $1,500. Each drone had a datalink and control software. The over one thousand flying drones coordinate autonomously and synchronize movements, with a flight precision of 2 centimeters horizontally and 1 centimeter vertically. If something goes wrong and a drone can’t reach its programmed position, it automatically lands.
In fall 2017, the Chinese Academy of Sciences used high-altitude balloons to release two shoebox-sized, flying-wing drones that flew downward from a height of 15 miles. They flew a distance of more than 60 miles. Those high-altitude micro UAVs have passive sensors for detecting electromagnetic activity and can map terrain. The USA has Perdix system drone swarms. The US has released them from military jets.