Of all the things airline passengers are asked to do before a flight takes off and lands — buckling our seatbelts, stowing our tray tables, returning our seats to their upright positions — opening the airplane window shades seems pretty incidental. Turns out it’s not.
A recent Reddit thread posted to the r/YouShouldKnow subreddit by a flight attendant under the username u/TerraFormer 001 explained that opening the windows before takeoff and landing is actually a matter of safety. The goal is to help the human eye adjust to the outside light to ensure that passengers can evacuate as swiftly and safely as possible in the event of an emergency, without wasting time trying to orient their vision. The poster noted that the cabin crew always turns off the cabin lights during takeoff and landing for the same reason.