If you’ve ever settled into your seat as a flight prepares to land, you might ask yourself, “Why do planes dim the cabin lights?” It can feel a little dramatic, sort of like the plane is setting a mood, but this isn’t an aesthetic choice. There’s a precise safety reason behind it, and it applies to takeoff too.
Dimming the lights is standard procedure during what aviation professionals call the critical phases of flight, which is the moments when, statistically, most in-flight incidents occur. “We dim the cabin lights before takeoff and landing mainly for safety,” says Anubha Jaiswal, a senior cabin attendant with IndiGo. “These are the most critical phases of a flight, and if there’s ever a need to evacuate, your eyes need to already be adjusted to the outside lighting conditions, especially if it’s dark outside.”
It comes down to a basic principle of human biology. The eyes take time to adjust from bright light to darkness. In an emergency, that adjustment delay, which can be anywhere from a few seconds to several minutes depending on the contrast, could make a critical difference. “When the lights are dimmed, your eyes adapt more quickly, so you can see emergency exit signs, pathways, and instructions clearly without that sudden adjustment delay,” Jaiswal explains.
There’s an outward-facing benefit too. Dimming the cabin also allows passengers and crew to see outside the aircraft more clearly, which proves helpful for spotting anything unusual on the tarmac or during approach. “It’s an important safety measure to ensure a faster and safer response in case of an emergency,” says Jaiswal.
The practice is mandated by both the FAA (Federal Aviation Administration) and EASA (European Union Aviation Safety Agency) for night operations, and most airlines apply it as standard procedure regardless of time of day, because even on a bright afternoon flight, conditions outside can change quickly on approach. It’s a small adjustment, but with a clear purpose. Because in the 90 seconds that aviation regulators say an aircraft must be fully evacuated in an emergency, every second of preparation counts.
This article was originally published on Condé Nast Traveller India.