If jetstreams go 1 way how can they speed up an air flight both ways in the southern hemisphere?

Jet streams go different directions at different altitudes. 32k-38k move very quickly west to east. About 200-250mph in the south. Up a bit higher 38k to 45k they jet stream moves east to west at 50mph. That’s why the flight Sydney to Santiago is 3 hours faster than the flight Santiago to Sydney.

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