Thank you scon10, Isaac, Sergio and John.
"I used to marvel at how the wings would flex in turbulence", this one made me smile.... First time I ever flew was in a Transavia Sudaviation Caravelle to Alicante in Spain, back in 1971. I was shit scared when I saw the wings flexing up and down during the flight, extremely afraid they would break off. My father, who was an aeronautical engineer, tried to calm me down by explaining the principles of aeroelasticity. Of course that did little to ease the mind of the seven year old I was at the time.... but somehow he must have made a point as I can't remember being scared when flying home again one week later
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Erik