Your methodology seem to exclude the fact that altitude=distance. The effects you claim are caused by the glass should also be noticeable from ground level when looking out at things more than 10km away. The very weak explanation that pilots 'flip a switch' doesn't explain how apparent horizon curvature increases with altitude, as more of the globe earth can be seen in our field of vision.

Also, your opening statement is a half-truth. Sure, people have attested to an unbroken, flat horizon, but people have also attested to being able to see the curve of an ocean horizon on a clear day.

The first 4 references are all pretty shaky, but reference #4 is a joke. If it's only available to people who agree with you, that's a pretty big red flag that it's bullshit that won't survive any scrutiny.

I think you're suffering from confirmation bias, or deliberately trying to mislead people.