Sorry, but you started explaining that this observation can be explained by windows lensing - unsupported claim - , perspective issue, - still unsupported claim- or an illusion , directly contradicted by my own experience.
Unfortunately, even if I flew Concorde once during a small supersonic loop trip, I could'nt see myself a curvature as I was located at the aisle seat, (and because these windows were awfully small !)
A close relative was a former Concorde flight engineer. He claims he routinely saw earth curvature at cruise altitude. I tend to believe his experience, and the link provided seems to agree with him.
So you're saying you've never seen curvature on a flight, even on a high-altitude flight on the Concorde. Thanks for your contribution.
Many people claim to have seen curvature on flights. I believe they have not. I'm not one to call anyone a liar, so I like to try to find alternative explanations. You seem to be villainizing me for that. I never made the definite claim that there is measurable curvature due to perspective, lensing, or illusion, but apparently because I'm ostensibly a "flat-earther" anything I say is a statement of irrefutable fact needs to be supported by maths and peer reviewed studies.
The appearance of curvature at higher altitudes, a la the concorde, is actually where I wanted this discussion to go, so thank you for bringing it up. Many sources cite measurable curvature at these altitudes, which I think is fascinating, really.
No I'm saying that during my single Concorde experience, I was not in a position allowing me to see curvature, nothing more, nothing less. From my perspective, it's inconclusive.
Your alternative explanations are always welcome, and I'm sorry if you feel villainised, but you should agree that this kind of statement :
Perspective and lensing through airline windows causes the apparent curve viewed on commercial flights at 30,000 feet or so
sounds quite like an irrefutable fact, whatever your favourite earth shape is.
Anyway, if we agree that some curvature is seen during 50 kft+ flights, let's dig a bit, why do you find it fascinating ?