See, now this is ridiculous... of course they make course corrections, but those corrections are done to maintain a regular altitude. You can google it.
Regardless, to totally discount their personal observations of seeing curvature and their belief that it exists, makes this flat-earth argument the stuff of lunatics.
They say it exists; you say it doesn't...fine, but their input is still valid, as valid as yours...
I'll believe the 1.5 million, you believe your 19.