So why has no flat earther hired a plane flown at 30,000 feet got as far they can get before having to turn around? at least they could confirm a minimum distance which the earth would stretch beyond the wall?
#1 it's illegal
#2 some have tried, and been shot down; others, simply vanished.
#3 HP Lovecraft predicted the above #1-2,
plus whatever shenanigans exist today, as well as
elder gods shenanigans, over 100 years ago.