If the earth was curving at 8 inches per mile like we're told then certianly the average plane going at 500 miles per hour would have to nose down every few minutes because if not they would very quickly be thousands of feet higher than intended. No pilot ever will tell you they account for curvature while flying. Neither do snipers, bridges, railways, tunnels, etc.

If the earth isn't flat, then tell me where the curve is at?