Why aeroplanes travel from Australia to America all way through the globe but not from Australia to America directly inspite of world being round in shape?

Answer 1

The shortest possible trip from Perth Australia to New York City measures about 11,600 miles. In order to
follow that route, you start out from Perth heading roughly to the northeast. You leave Australia at Darwin
on the north coast, then continue across New Guinea and the atolls of the South Pacific, and across the Pacific
toward Alaska. Your route runs only about 100 miles south of the Aleutian Islands and parallel to the chain,
and enters North America between Juneau and Sitka, Alaska. At that point, the route is pointing to the East.
As it crosses Canada, the route is north of Edmonton, Saskatoon, Regina, Winnipeg, Thunder Bay, and Toronto.
After crossing Lake Ontario, it re-enters the USA at Rochester NY pointing southeast, and proceeds across
New York State, to New York City.

That's the shortest possible route from Perth to New York City.

From Perth, if you wanted to travel the shortest route and end up in Montreal instead of New York City,
you'd cross the tip of Siberia, the north coast of Alaska, and Hudson's Bay in northern Canada. And although
Montreal is 330 miles north of New York City, your trip from Perth to Montreal would be 300 miles shorter
than your trip to New York.

You can verify each of these routes ... and any other "shortest" route you'd like to investigate ...
by stretching a rubber band on a globe between your start-point and end-point.