While not everyone will have pondered the subject while staring out of the window during a flight, the question as to why aeroplanes have circular windows rather than square ones is interesting.

Over the years, aerospace engineering has made huge leaps in aeroplane technology, meaning planes can carry more passengers and go faster. The planes have also changed shape to increase safety – including the windows.

In the 1950s, when jetliners were starting to become mainstream, the de Havilland Comet came into fashion. With a pressurised cabin, it was able to go higher and faster than other aircraft.

The strangest airplane patents Show all 4 1 /4 The strangest airplane patents The strangest airplane patents The saddle seat, proposed by Airbus Operations in 2013, in which the customer sits in a fold down seat more akin to a bike seat than a chair. Back and neck support free, of course. Airbus Operations The strangest airplane patents Proposed in 2014 by Zodiac Seats France, an aeroplane seat manufacturer, the Economy Class Cabin Hexagon makes passengers sit in alternating backward and forward facing seats in an attempt to maximise space and minimise the chance of avoiding eye contact. Zodiac Seats France The strangest airplane patents Filed for patent in 2013 by The Boeing Company, the Upright Sleep Support System is deployed from a backpack that sits on the chair and is designed to allow passengers the chance to lie face first onto it, with a massage table esque cut out for your face. The Boeing Company The strangest airplane patents The newest patent proposed by an airline, this new arrangement of seats was put forward by Airbus Operations GmbH in 2015. Developed as a way to maximise space, the arrangement and design allows passengers to recline to a horizontal position by pushing the leg rest down. Airbus Operations GmbH

However, the plane had square windows and in 1953 two planes fell apart in the air, killing 56 people in total.

The reason for the crashes? The windows.

Where there’s a corner, there’s a weak spot. Windows, having four corners, have four potential weak spots, making them likely to crash under stress – such as air pressure.

By curving the window, the stress that would eventually crack the window corner is distributed and the likelihood of it breaking is reduced.