What happens if the door opens mid-flight? Why do seats and tray tables need to be upright during takeoff and landing? What causes the white trails planes leave in the sky? Why do window shades need to be open during landing? Are electronic devices allowed on airplanes?

Every year more than 36 million commercial flights take to the sky and that number is only growing. Air travel can get confusing if it’s your first time and there are a lot of things even frequent fliers get wrong. So, to help you out, here are the answers to several questions almost every passenger has.

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