Before that, the hijacking of U.S. drones in Iran was a humiliating experience. Iran not only cracked the technical secrets of U.S. drones, but also wantonly flaunted them through video. So NASA learned from the experience and developed a kind of UAV made of fungus, which can be destroyed by itself, making espionage disappear.
NASA Ames Research Center has developed a biodegradable UAV, which is made of mycelium. No one knows that if the plane keeps flying or sprinkles some sugar water, it will disappear in an instant.
But this experiment has not been completed completely. Many parts of the UAV can not be replaced by this material. At the same time, many parts of the UAV are made by 3D printers.