I am under the belief that many of the flights are based more on practicality rather than ideal paths.
Why would you set up a flight route across the potentially dangerous barren Arctic when it makes more sense to stay near more of the habitable zone containing airports, islands with airstrips, and also make money picking up and dropping off passengers on the way?
I also believe that there are many factors to consider other than geography, such as jet streams and trade winds. Some flights also make unscheduled stops for a variety of reasons. We had some news articles somewhere of people on supposedly non-stop flights complaining that the plane stopped for fuel.
In addition, there were some articles describing that planes can and do travel at supersonic ground speeds on a regular basis. And other articles saying that the given flight times are overly padded with a large amount of extra time to ensure on-time arrival. I'll see if I can dig those up.
In regards to the edge, I would say that is unknown what would happen, or where that might be. The subject of air travel is a topic of interest and discussion, but ultimately unknown what the variables are or what can be trusted, which I believe is holding up development of the FE world models like the
bi-polar model.
When you ask me about air travel and its applicability to the shape of the Earth, you may as well ask me about busses in China, who might be traveling at different speeds for different reasons, on non-ideal paths for different reasons, and may not be accurate in the times or stops for various, not necessarily nefarious, reasons. That's a business enterprise based on money and practicality, not a reliable scientific instrument to determine the dimensions of the cities.
If someone suggested to you that you should know the dimensions of Shanghai based on such questionable data you would probably find absurdity in that assertion.