What are holes in plane windows for? Flight attendant explains

Gazing out of a plane window is one of the small joys in life, a moment we associate with heading on holiday and enjoying some well needed R&R. But what are those tiny holes in the glass?

Usually found at the bottom of a window, the very small gaps in the plane windows come as a bit of a surprise at first glance.

If you are a nervous flier its enough to put the heebie jeebies in you. But calm down everyone, the hole exists for a very good reason.

Just ask any flight attendant on your aircraft and they'll explain to you.

But we're here to answer that before your next flight, thanks to one air steward over on TikTok.

The hole stops the window from freezing over (Getty Stock)

Henny Lim, who is an air steward for the Philippines-based airline Cebu Pacific, always has passengers asking her about those strange little holes in the window.

In a video shared to TikTok, she explained they’re called ‘bleed holes’.

And they’re quite important too as Lim wrote in the clip: “The tiny hole helps to balance the pressure difference between the cabin and the outside air.”

The flight attendant adds it has another purpose in releasing ‘moisture’ and stopping any ‘frost or condensation’ from blocking your view as you gaze out into the sky on your journey.

The Federal Aviation Administration (FAA) also confirmed the importance of the bleed hole to Business Insider, with the reason going beyond frosted glass and air pressure to the integrity of the plane's structure in the case of an emergency.

It said: “Airplane windows consist of three separate panes. The outer pane deals with this air pressure difference. Thanks to the tiny holes in the middle pane, known as the 'bleed hole.' Its primary purpose is to balance air pressure.

“The ‘bleed hole’ allows pressure to balance between the passenger cabin and the air gap. Meaning the outer pane takes on the pressure while the middle pane acts as a fail-safe.”

Bleed holes are fail-safes should cabin pressure drop (Getty Stock Images)

Plus, like Lim said, the FAA explained it releases moisture from that air gap to prevent the window ‘from fogging up or frosting over’.

Something you might not have given as much thought as the holes is why the windows are round and not square - and the reason is a little horrifying.

Back in 1945, a flight from Rome to London suddenly exploded in the sky and a few months later, a similar incident took place from London to Johannesburg.

The one thing both aircrafts had in common was that their windows had sharp squared-off corners.

So, The Telegraph did an investigation into the twin tragedies, and found that the square shape of the windows resulted in metal fatigue. Specifically, the sharp corners would put more pressure on parts of the plane in high altitudes.

Airlines then changed the designs to more circular windows, as this allows the stress on the metal to flow more evenly around the edges.