45) On a ball-Earth, Johannesburg, South Africa to Perth, Australia should be a straight shot over the Indian Ocean with convenient re-fueling possibilities on Mauritus or Madagascar. In actual practice, however, most Johannesburg to Perth flights curiously stop over either in Dubai, Hong Kong or Malaysia all of which make no sense on the ball, but are completely understandable when mapped on a flat Earth.

Re accessing Madagascar from Australia, there are direct flights from Perth to Jo'burg, with no stopovers to refuel, then a lighter plane from Jo'burg to Antanarivo. Then Perth's latitude is -31 while Joburg is -26.
Interestingly, the east-west flight takes 10hr 45min while west-east flight takes 9hr 20min over the same distance. An hr 25min difference, which is greatly appreciated if your travelling with a full load of passengers.
I do believe that there are practical concerns such a demand and marketing that play a large parts in necessary diversions, e.g. you cannot fly direct Sydney-Antanarivo simply because the demand is not there.