Originally Posted by
Joroy70
Is this Valid
YYZ-AUH-SIN
MNL-AUH(STOP)-YYZ-SJO
It should be - assuming YYZ-SJO on AC is combinable with the other flights.
If not you may have to look at Copa
And to your earlier question - it has nothing to do with backtracking east/west - but every thing to do with combineablity of AC flights with partner flights. Sometimes its just not possible, either to dynamic pricing or route restrictions