Revealed: Why window shades have to be kept open during takeoff and landing

Passengers are always asked by cabin crew to raise their blinds at the start and end of every flight

If you've ever wondered why the window shades in an aircraft have to be kept open during takeoff and landing, we can now reveal the answer.

Passengers are asked to take this step so that cabin crew members can look out of the windows to assess which side of the aircraft is safest to disembark from in case of an emergency .

Aviation safety officer Saran Udayakumar explained on question-and-answer website Quora that the window shade opening is "a part of a long process to prepare the cabin for sudden unexpected emergencies."

The opening of the shades, along with the folding up of tables and putting seats in upright positions helps the cabin crew evacuate all passengers - a procedure for which they only have 90 seconds in total.

Windows have to be kept open during takeoff and landing due to emergency procedures

In case of sudden emergencies, "every second counts," Udayakumar wrote. "Therefore if shades are open crew can easily see outside conditions to help them in planning the evacuation (which doors to use for evacuation etc.)."

Emergencies are more likely during take offs and landings, he said, adding that "during daytime, opening window shades and putting cabin lights to full makes the eyes used to sunlight so if something goes wrong and passengers need to be evacuated there will not be sudden change in light contrast which might lead to temporary blurred vision."

The same principle applies to night flights, he said, with window shades open and cabin lights dimmed.