Flight secrets: Why are plane windows always round?
Many passengers may have also noticed that plane windows are always round, despite windows in buildings normally always being square.
This was brought into place in the 1950s and the reason behind it has nothing to do with aesthetics.
So why are plane windows no longer square?
Two plane crashes in 1954 were the catalyst to changing the shape of the windows from square to circular
Two plane crashes in 1954 were the catalyst to changing the shape of the windows from square to circular.
The de Havilland Comet was the world's first commercial aircraft which first flew in 1949 and was a revolutionary change in the aviation industry.
However, it suffered from two plane crashes in 1954 which proved its downfall and changed the way in which planes are designed.
Flight 781 from Rome exploded just 20 minutes after taking off, whilst Flight 201 to Johannesburg crashed into the Mediterranean sea just months later.
Flight secrets: The de Havilland Comet suffered two major plane crashes after design problems
An investigation which was launched found that the crashes were due to structural weakness and metal fatigue of the plane.
Cracks were found around the doors and window apertures as the fuselage pressure meant the plane was blown apart.
The angles of the square windows showed that the pressure was three times greater than anywhere else in the cabin.
After the investigation, de Havilland made changes to the windows, making them rounder which set the precedent for all other aircraft designs to follow to reduce the pressure.
Flight secrets: The de Havilland Comet had two crashes in the same year
Flight secrets: Windows are now always round to avoid pressure on the corner
Sadly, the airline never recovered and retired in 1997.
Other aircrafts quickly followed with the new designs, with the first Boeing 707 flying in 1954 with the new designs.
Another way in which an aircraft controls the pressure is with small holes in the window.
This means that even if the outer pane of a plane cracks, the pressure can be maintained by an inner pane.