The 400 feet rule for drones refers to the maximum altitude limit set by aviation authorities in some countries, including the United States, to ensure the safe operation of drones in shared airspace. According to the Federal Aviation Administration (FAA), recreational drone pilots must fly their drones at or below 400 feet (approximately 120 meters) above ground level (AGL) to minimize the risk of collisions with manned aircraft and to maintain the safety of the airspace.