It's not to set the mood.
No matter the airline, the departure airport, the destination, or the time of day, travelers can rely on a few familiar features on every flight.
Like the safety demonstration, the lowering of cabin lights and raising of window shades during takeoff and landing—the most critical moments of every flight—is standard protocol.
But what purpose do these seemingly arbitrary actions serve? As it turns out, they're standard safety measures.
The dim lighting is a precautionary measure that allows passengers’ eyes to adjust more quickly during an emergency evacuation.
“Imagine being in an unfamiliar bright room filled with obstacles when someone turns off the lights and asks you to exit quickly,” said Chris Cooke, a pilot with a major domestic carrier.
And in a true crisis—if the cabin is filled with smoke or the power goes out—it's easier to see the emergency lights lining the aisle and the exit signs in a darker cabin.
Similarly, raising the window shades fills the cabin with natural light, and help travelers orient themselves during an emergency. Being able to see the conditions outside—especially during a 90-second evacuation—can help passengers get to safety.
Unobstructed windows will also make it easier for first responders assisting from outside to assess the situation, aviation safety officer Saran Udayakumar noted on Quora.
Chances are, anything that seems trivial on an airplane—like those tiny holes in the windows—is designed to keep travelers safe. Even the ashtrays in airplane bathrooms, which you probably thought were vintage details, are required precautionary equipment.
So the next time the captain dims the cabin lights and your flight attendant reminds you to lift your window shade, remember it's all in the name of safety. And then enjoy the view.