<font face="Verdana, Arial, Helvetica" size="2">Originally posted by braslvr:
But the flip-side if I'm correct is, if you are using a customer service issued "one segment international upgrade coupon", you can use it all the way from LAX to SIN, even though you change planes in HKG. 
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Yes. Technically speaking if you flew LAX-DEL via HKG and it was issued as one flight coupon, you can get to DEL with a one-segment upgrade. In practice, you can usually use the one segment upgrade all the way even if you were issued two flight coupons.