But why? Does the shape actually help the plane stay up, or are the curved edges just more aesthetically pleasing? And if you flew in the early days of air travel, you’ll question it even more. Plane windows used to be square.
It turns out, when airplane windows were square, the planes flew slower and lower. As flying became more popular, airlines began to fly at higher altitudes to cut costs (there’s less drag up there, which limits unnecessary fuel use). The planes themselves also had to be increasingly pressurized.
That’s when square windows began to prove deadly. Two planes disintegrated in midair because of stress concentrates caused by the sharp edges of their windows. The analysis of each crash led to the oval design you see today. (This is how to survive a plane crash, according to science.)
With this new and improved shape, stress can flow smoothly, and we can fly safely. For more on this fascinating but significant detail, watch the video below.