Hi all, I have a maybe niche question: 10/24 CUN-IST-KIX, long connection at IST, with IST-KIX leg departing on 10/26. Check-in for 2nd leg more than 24 hours after CUN-IST departure. (for 6-continent challenge, and 10/26 is basically last date that I feel comfortable to schedule the Asia flight).

The IST-KIX showed no C-to-R class inventory at booking (but I upgraded CUN-IST at booking). And at the moment show Y-below with 9+ available. A few days after booking the ticket (and still weeks before departure), ExpertFlyer notified and showed C1 availability. I checked app and no Upgrade options. I then proceeded to book a refundable IST-KIX with the last C class.

Suppose I want to cancel the later purchased C-ticket, and do a (Last Minute?) upgrade by Miles, has anyone done this or similar? In a September flight, BOS-IST-SYD, I also was only able to upgrade in advance for the BOS-IST leg, but not IST-SYD. A C class for IST-SYD opened up after I checked in the BOS-IST leg, and the call center was not able to upgrade me before the flight. During the flight, I was even able to purchase (and cancel, an hour before landing) an IST-SYD, C class ticket. But by the time I got to IST airport and talked to the ticketing desk at the M&S Lounge, the C class was taken/assigned (it was a completely full flight, so the IST-KUL-SYD in Economy row 10 was really quite unpleasant).

If anyone has some idea on the optimal timing (say 1 hour before the first leg CUN-IST and try the App or call) to cancel the IST-KIX C class ticket, and apply mileage upgrades on the separate ticket, that'd be very much appreciated. (or am I doing something bad by buying 2 tickets with the intend to cancel one?) Thanks in advance!