If you've landed at - or flown from - Birmingham Airport recently, you'll be familiar with this message.

Flight attendants will routinely tell you to open your window blinds when you're coming into land.

And, apparently, the reason for this is actually fairly scary.

Cabin crew make you open plane window blinds for a very good reason, it turns out.

Flight attendants have revealed that they urge you to lift the shutters to help your eyes acclimatise to the lighting outside.

This is seen to be crucial if the aircraft is evacuated during an emergency.

It means those flying aboard the aircraft can establish what’s happening outside, too.

Aviation Safety Officer, Saran Udayakumar recently revealed more about the rule in a Quora thread.

He explained: “In case of sudden emergencies, every second counts.

“Therefore if shades are open crew can easily see outside conditions to help them in planning the evacuation – which doors to use for evacuation.”

David Robinson, an Aeronautical Industry Professional, wrote: “If you've somewhat acclimatised to low light conditions before an unfortunate incident occurs, you'll have a visual capacity which initially may exceed 1,000 times better compared to if you were suddenly plunged into the darkness and had 90 seconds to disembark from the aircraft”.