The balls on power lines serve as visibility markers to make the power lines more visible to low-flying aircraft like planes and helicopters. They are spherical visibility markers, specifically in “aviation orange, white or yellow,” and are required by the Federal Aviation Administration (FAA) . The conductors and skyline wires become almost invisible against the terrain when flying, and helicopters and small planes often fly low in mountain passes or over freeways while approaching airports. The balls are placed on power lines to make the conductor crossings visible to aircraft pilots, and they are critical to protecting the electrical infrastructure. The balls are also placed on electrical wires on major freeway crossings near airports for the same reason. The diameter of the balls must be at least 36 inches on wires that cross canyons, lakes, and rivers, but the FAA allows 20-inch spheres on power lines fewer than 50 feet above ground level and within 1500 feet of an airport runway end. The balls on electricity lines help prevent life-threatening injuries, wildfires, and power outages.