The earth is flat not spherical

My opponent starts out with a weak rebuttal to the descending plane argument, and ignores the entire rebuttal about circumnavigation. Where his math comes from is beyond me, so let's do some real math. Planes fly at an average of 500mph, this translates to about 8.3 miles per minute. The curvature for 8 miles is 42 feet. This means the plane descends 42' per minute. If my opponent thinks this isn't noticeable, he is entirely mistaken. Please explain where you get 3 degrees. By the calculations stated here, in 500 miles, or one hour in a plane, you have to descend 378 MILES. Math is here: 500 x 500=250,000 x 8= 2,000,000 ft converted to miles is 378 miles. 3 degrees? Please explain further. Planes fly level with the horizon the entire flight. So I ask again, is it more plausible that planes fly around a huge circle, or descending 378 miles per hour? Please have common sense in this decision, it seems my opponent will deny this argument to the end. 1.Flight paths. My opponent explains that flight paths go thousands of miles in the wrong direction because of weather! This is ridiculous, planes can either ascend above storms, or simply go at most a few hundred miles around any storms, which are carefully watched to avoid any "death wishes". Since the distance from Chile to North American airports is at least 5,000 miles, on a path almost going away from the destination, this is a silly assumption , especially since ALL flights take the same path, regardless of weather conditions. 2. Curvature Since this isn't an actual argument, and my opponent agrees the numbers are correct, no further discussion is needed. 3. Distances sighted. My opponent takes the stance that the picture above is only a mirage. A superior mirage to be exact. I challenge anyone reading this to research mirages, Google pictures of superior mirages, you will not find any pictures that aren't distorted, inverted, etc. as I stated before. Also note how mirages only appear during "special circumstances" and rarely happen so that the entire city appears clear, upright, and undistorted. With this in mind, please look at this time lapse from the same spot. https://youtu.be... People in the region say they can see it most of the day. I guess conditions remain "just right" all day long. 4. Reflections on water. My opponent is trying to "keep in mind" that water somehow curves when I have shown the opposite in all my proofs. He, however has provided nothing to prove his case and his burden of proof has not been met. He states that "the earth's curvature isn't significant enough for it to affect the reflection of the sun in the water" yet in the experiment above, even the slightest bend will not produce the reflection described. Also, my opponent agrees with my preface on the curvature of the earth which states that "the surface of all standing water must have a certain degree of convexity--every part must be an arc of a circle". My opponent's closing statement is confusing, in that he has not offered any of these "countless other possible retutations". Going into r4, it stands that my opponent has dropped circumnavigation, and has not refuted my proofs satisfactorily.