The routing changes daily. The software tries to give the fastest flight time using the winds available and so doesn't always follow the great circle track. In some cases, dispatch will change the routing from the software to avoid us flying through tropical cyclones or volcanic ash.
On some flights I've been as far north as the Marshall Islands and as far south as Tahiti.
It always sucks flying a northerly track into MEL only to see my house sailing past in Sydney, knowing I've gotta come back again after the flight but that's life.
