There's a number of safety precautions flight attendants must follow before taking-off.
Now one of the steps before hitting the runway and landing is having the lights dimmed.
While you may not have noticed this little step, others are aware cabin crew always dim the lights during these two stages of a flight. Some theories on social media say this is to reduce light pollution in the sky, but that's not the case.
Pilot and author of Cockpit Confidential Patrick Smith said this is down to a precaution in case of an emergency.
He said: "Dimming the lights allows your eyes to pre-adjust to darkness, so that you're not suddenly blinded if something happens and the power goes out, and you're dashing for the doors in darkness or smoke.
"The emergency path-lighting and signs will also be more visible. And it makes it easier to see outside, which helps you to maintain at least a basic sense of orientation – i.e. which way is up."
Meanwhile another pilot, known as Rohan Bhatnagar, backed this claim up in a post on Quora.
He said on the site: "It is a safety procedure for the aircrafts. The probability of crashing is higher during the take-off and landing."
He concluded: "During a crash when the lights go out it takes time for the human eye to adjust to a complete blackout, so the lights are dimmed such that in case of an emergency, the passengers can be evacuated quickly.
"It is also dimmed so that in case of emergency the fluorescent directing lights in the aisle come on and are clearly visible to the passengers."
Emergency paths: Reduced cabin lighting makes emergency exit signs and floor path markers easier to see.
Night vision adjustment: It can take around 10-30 minutes for your eyes to adjust to darkness so these dimmed lights mean it's already adjusted to dark conditions.
External assessment: Lower light levels help passengers and cabin crew see potential danger outside, like engine fire or smoke.
Power conservation: Although this is minor but decreasing lights helps to conserve engine power during critical high-power moments like take-off and landing.
