When an airplane’s cabin lights dim, well-conditioned air travelers instinctively know that the flight has been cleared for takeoff, or that it's in the final moments of descent before landing. While the lowering of cabin lights is widely accepted as a safety procedure, what purpose does it actually serve? Part of the reason for dimming the lights is that it conserves engine power and puts less strain on it, which means an aircraft can shorten its takeoff roll and become airborne sooner. However, the primary reason for a change in cabin lights is directly connected to why the crew asks passengers to raise their shades: safety. In case of an emergency, it can take our eyes between 10 and 30 minutes to fully adjust to a dark setting. Dimming the lights can help eyes pre-adjust to lower light. Those few seconds could make all the difference if exiting the vehicle becomes a necessity. In dimmer light, emergency lighting and illuminated pathways will be more visible as well.
