To understand this issue look these routes and track logs.
This is a different route from West to East and East to West.
Adelaide to Sydney gets about 1:25
But opposite route gets about 1:55 hours.
Difference about %25.
Look to track logs.
These plains are both Boing 737 so we are waiting that planes goes on same altitude about equal speeds or it must be about. But one of them is about halkf of the other.
This is first plane:
Going from
Adelaide to Sydney with about 1.080 kmh on 37.000 altitude.
This is the second one:
Going from Sydney to Adelaide with about 640 kmh on 38.000 altitude.
Same plane, same route.
It's like something resisting to second plane as a power stronger than air friction or another acts. How is it possible?