A few days ago I flew on an A321. While pointing to something outside my finger touched the window. It made a crackling sound and felt quit flexible. I was able to push it at least 5mm without any effort (I didn't wanted to push further because I thought I might break it).

On the way back, I flew on a B737 and the same thing applied on its windows as well.

I'm pretty sure it's that thin because of the weight but is there any other reason for such a thin (and probably fragile) inner glass which could be easily damaged by a passenger by mistake?

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    $\begingroup$ Just to put your mind at ease - there is no way you would have broken it. It would be a heluva coup for terrorists if they could depressurize an aircraft with little more than a window seat and their bare hands :D $\endgroup$
    – Jamiec
    Sep 12, 2017 at 8:58
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    $\begingroup$ It's not the real window, behind the panel that you pushed are one or two layers of hard transparent material that you won't be able to easily deflect. Also refer to this answer. $\endgroup$
    – Koyovis
    Sep 12, 2017 at 9:03
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    $\begingroup$ It probably is Polycarbonate, way stronger that you think... $\endgroup$ Sep 12, 2017 at 9:09
  • $\begingroup$ I'm aware of the fact, that there are more than only this layer of glass and that the outer layer is thicker. I was just surprised that is was that flexible. $\endgroup$
    – merspieler
    Sep 12, 2017 at 9:33
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    $\begingroup$ The layer you touched is just an inexpensive and easily replaced screen to keep passengers from scratching up the costly and more permanently installed transparent pressure bulkhead. - I am guessing the flexible inner screen can be replaced without the level of re-certification required to replace the pressure resistant panes. $\endgroup$ Sep 12, 2017 at 12:55

1 Answer 1


The inner window is just a plastic protective cover, so that you don't touch the glass, which is probably very cold at altitude. You'll notice on the inner window there is a tiny hole at the bottom to equalize pressure and prevent condensation.

enter image description here

See this article that explains it


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