Lowering cabin lights and raising window shades are standard safety measures during takeoff and landing—the most critical moments of every flight. But what purpose do they serve? As it turns out, the dim lighting is a precautionary measure that allows passengers’ eyes to adjust more quickly during an emergency evacuation. As Chris Cooke, a pilot with a major domestic carrier, puts it: “Imagine being in an unfamiliar bright room filled with obstacles when someone turns off the lights and asks you to exit quickly.” The raised window shades bring natural light into the cabin, just in case it’s needed.