Miles upgrade by segment vs full itin?
 

I've done a couple of searches, but it was hard to find the best terms. My situation is this: I'm flying YYZ-DXB-HKG (Business Flex). YYZ-DXB upgrade requires 54,000 miles, and DXB-HKG requires 39,000. YYZ-HKG requires 67,500 for the whole trip.

My question is: if only one segment is open for u/g and I book it, then the other segment opens up, does the total requirement revert to the 67.5K or do I have to cancel and rerequest to get that?

Unfortunately you have to cancel and request - best to do that over the phone so when they cancel the first sector they hold the inventory open for you! The mileage refund is also pretty instant that way, as well.

just did that today without hassle. The operator upgraded my second leg and charge me the difference to the total cost for two legs instead of the cost for each individual leg. Saved me 20k miles