Why Do Airplanes Have Rounded Windows?

Safety first.

Holly Large - Editorial Assistant

Holly Large

Holly Large - Editorial Assistant

Holly Large

Editorial Assistant

Holly is a graduate medical biochemist with an enthusiasm for making science interesting, fun and accessible.

Editorial Assistant

Airplane window. Mountain and clouds view

Some airplane windows used to be square – but this was a fatal design flaw.

Image credit: Michaelvbg/

Turns out there’s more purpose to the design of an airplane window than allowing for aesthetically pleasing birds-eye-view photos or staring out of them pretending you’re in a music video. There’s a reason why they have that little hole and why we have to keep their shades up during takeoff. But what about their most characteristic feature: Why are airplane windows rounded?

If you ask a small child to draw an airplane, they’ll more than likely draw the passenger windows as little ovals, but planes haven’t always looked that way. The de Havilland Comet, an early commercial jet design, had square windows. But within just five years of their introduction, three Comets had a series of tragic crashes.


After the third crash in 1954, investigations determined that all three crashes had been caused by cracked window frames, as a result of their square design. It was revealed that square windows deal very badly with the stress caused by the increasing cabin pressure that comes with high-altitude flying.

However, high altitude is a necessary element of commercial flight – up high in the sky, there’s less drag, which in turn means less fuel used. That’s ideal for airlines because it saves them money and reduces the impact of flight on the environment (although scientists are looking into alternatives to traditional fuel). There’s also less turbulence at higher altitudes, which makes for a more comfortable flight.

So what was the solution? Swap those squares out for ovals. This helps to evenly distribute the pressure exerted on the window and thus reduce the likelihood of cracking.

“The narrowest part of the oval will be designed to ensure the curve does not generate unsafe stresses in the surrounding material,” explained Dai Whittingham, chief executive of the UK Flight Safety Committee, speaking to MailOnline Travel. “Recently we have started to see some designers opting for more rectangular shapes, but these will always have curved corners.”


Besides the element of increased safety, there are still some more superficial benefits. “Designers prefer oval windows because they can get a larger viewing area which suits the biggest range of passenger sitting heights,” said Whittingham.

Check out this video by the YouTube channel Real Engineering, which explains the physics behind this engineering quirk that has puzzled air travelers ever since.

An earlier version of this article was published in January 2016.


  • tag
  • pressure,

  • airplanes,

  • physics,

  • history,

  • aviation,

  • Engineering,

  • design,

  • Windows