This is only the second post I have ever made, but I will make it brief because this is a relatively simple issue that I think needs to be resolved.
Many of the Flat Earth proponents on this site reached the conclusion that the Earth is flat on the basis that it appears flat to the senses. All data therefore must point to the fact that the Earth is flat, or else be disregarded or discarded as part of the conspiracy. I don't mean to address this type of thinking in this post. Whether you agree with this train of thought is your own business and irrelevant to the topic at hand.
The issue I see is that the Earth appears to the senses precisely as one would expect it to if there Earth were indeed round. This has been acknowledged by FE'rs and RE'rs multiple times, and is reason why we have reached a consensus that not seeing a curvature in the horizon from an airplane does not disprove RET. An airplane simply does not go high enough for somebody living on a Round Earth to be able to see a curved horizon.
However, if the Earth actually appeared to be flat, you would be able to see the entire Earth from a suitable height (such as mount Everest). Likewise, when I walk from my apartment down to Lake Ontario, I should be able to see New York (And why can I only see the tops of those ships? Surely they aren't sinking as they move away from me, are they)? I know that there are a host of different theories to explain why we cannot see the whole Earth (bendy light, atmosphere thickness etc.), but the issue here goes back to the initial premise of FET.
Flat Earthers believe the Earth is flat because it appears to be flat.
The only problem is... it doesn't.