Originally Posted by TiteG4
Not so much a rule as the 'limitations' of network connection. From OWE T/C:
In any case, I tried to book SYD-LAX-ORD-DEL-HKG-SYD with AA RTW desk. As previous posts indicate, AA considers this routing as XONE4. According to the AAgent, ORD-DEL is 'over' Europe and hence it counts as North Am-Europe-Asia

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Isn't that just because there are no OWE 3 continent fares from Australia? What if you tried to book such a thing starting in Asia or North America, where 3-continent fares exist?