Why do the airplane need windows?

Answer 1

The primary reason is for passenger comfort and convenience. But there are three other reasons.

First, the windows allow emergency personnel to see inside the passenger compartment in the event of an emergency. This allows them to see where passengers are, whether there's fire or smoke inside the cabin, and so on.

Second, the windows allow the passengers and cabin crew to see outside the aircraft during an emergency. This allows them to see which evacuation paths are safe and which exits are blocked by fire.

Third, the windows allow passengers to remain oriented to outside conditions. Studies have shown that if the windows are closed (or presumably if you didn't have them at all), in an emergency evacuation, each passenger trying to leave the aircraft pauses as they reorient themselves to outside lighting conditions. Having windows open reminds the passengers that they are in a plane and that it is light, or dark, outside. This permits them to exit the plane much more quickly because they are moving from one familiar environment to another.