A few years ago, I wrote my autobiography and posted on here about the Comet in which I flew in the early sixties. I mentioned that the early Comet had "square" style windows and it was at the corner of these that the problems of metal fatigue became evident. Here is the link to Wikepedia which will verify the existence of the square style windows which led to the castatrophic failure of the airframe on more than one Comet.
https://en.wikipedia.org/wiki/De_Havilland_Comet
It is a very interesting account and shows just how much has changed in the past 50 - 60 years.