At the beginning and end of the flight or when it is dark outside, cabin lights are often turned off and passengers are asked to close the window shades.
The lights in the cabin turn off when the plane is on the runway preparing to take off and the process repeats at the end of the journey, signaling an imminent landing. The fundamental reason behind this process is the safety of passengers and crew, according to Simple Flying.
Cabin lights dim and then go out for the same reason the crew asks passengers to close the window shades, which is to ensure safety in an emergency. In such circumstances, ideal vision can make a key difference to human safety. Opening the window curtains also helps passengers determine direction in an emergency situation because they will pay more attention to their surroundings.
The human eye takes about 10 – 30 minutes to fully adjust to darkness. Turning off cabin lights gives passengers and crew more time to adjust to low light conditions. This is essential if the plane needs to be evacuated at night. In fact, the amount of time it takes the human eye to adjust to low light conditions can make a difference in the chances of escape in an emergency.
Another reason to turn off the cabin lights is that the darker the cabin, the easier it is to see the emergency lights and illuminated aisles. Therefore, everyone on the plane will be more fully prepared to evacuate quickly and safely. According to Colin C. Law, assistant professor of aviation business management at Stamford International University in Thailand, cabin lights are adjusted appropriately according to outside lighting conditions. For example, when evacuation is necessary during takeoff, the cabin lights should not be turned on in the brightest mode to avoid affecting the travel process.
Turning off the lights is also often associated with pulling the window shades on the plane. During the day, the following measure ensures the cabin is flooded with natural light, helping to increase visibility. Of course, in most cases, emergency situations do not arise. Finally, airlines turn off cabin lights during takeoff and landing to reduce the aircraft’s power consumption, optimizing engine performance during critical flight periods.