Shanghai, China and Buenos Aires, Argentina are a near antipodal pair. Both are located at the diametrically opposite points to each other on Earth’s surface. Therefore, we can fly from Buenos Aires in any direction and arrive in Shanghai after traveling a roughly similar distance, regardless of the course taken.
Any flight between an antipodal pair has a similar duration even though the different flights have different directions. This fact is only consistent with spherical Earth and cannot possibly be explained if Earth is flat.
As an example, on a flat Earth, the flight trip Shanghai–New York–Buenos Aires is almost a straight route between the two locations. Meanwhile, Shanghai–Auckland–Buenos Aires involves a massive detour, and it should take much longer than the aforementioned straight route. However, contrary to what is expected in the flat Earth model, both routes have a similar flight duration. Indeed, the Auckland route saves us about two hours compared to the New York route.
These flight durations were from Google Flights in October 2019.
- Shanghai–Addis Ababa–São Paulo–Buenos Aires: 11h 30m + 12h 5m + 3h 15m = 26.83 hours
- Shanghai–Doha–Sào Paulo–Buenos Aires: 10h 5m + 16h 10m + 3h 5 m = 29.33 hours
- Shanghai–Istanbul–São Paulo–Buenos Aires: 11h 50m + 13h 40m + 3h 5m = 28.583 hours
- Shanghai–London–Buenos Aires: 12h 5m + 14h 0m = 26.083 hours
- Shanghai–New York–Buenos Aires: 14h 20m + 10h 55m = 25.25 hours
- Shanghai–Dallas/Fort Worth–Buenos Aires: 13h 10m + 10h 23m = 23.55 hours
- Shanghai–Los Angeles–Buenos Aires: 11h 50m + 11h 58m = 23.8 hours
- Shanghai–Auckland–Buenos Aires: 11h 20m + 11h 45m = 23.083 hours
- Shanghai–Sydney–Buenos Aires: 10h 35m + 16h 4m = 26.65 hours
The Sydney–Buenos Aires route is no longer operational. The flight duration is taken from FlightAware data of flight ARG1180.