Honestly I don't believe that there is any evidence he or other can provide that will be concrete enough for some because their minds are made up...private jet, balloon or whatever. BTW, there are videos of smaller planes and the pilots saw the same thing, so private plane won't make a difference. There are also numerous balloon shots as well. Same thing...flat, even though, from the math, they should see the curve at that particular altitude. From my understanding, D Marble posted the video or experiment because someone or some people suggested that he "just look out of the window" and he will see the curvature. That didn't happen. Ironically I just came across pictures I took from an April flight I was on and it is flat.