My customer first mentioned (I don't recall why) that he couldn't see the Earth's curvature from an airplane. I said, "Sure, that's because you weren't high enough. You can see it from a high altitude balloon, though."
"Oh, those are all fakes. Illuminati Freemasons Nibiru blah blah blah...."
Your Flat Earther must know my Flat Earther. Lol
Next time I see mine I’ll ask her about satellite communications.