The earth is spheroidal, but Everest is only around 29,000ish feet. I think that may be lensatic distortion, it can be produced in reverse too, and to truly start to see the real curvature you have to go higher. Supposedly you could see it from a Concorde at 60,000 feet.
And then there's the live footage from takeoffs and even of rockets taking off shot by craft already in orbit, but that's flogging a dead horse.