Originally Posted by
StayingHomeIsBetter
Unless policies have changed, recall that "upsales" (e.g., purchasing the upgrade off of the seat assignment page) carry a risk.
If something happens that prevents you from occupying a FC seat on the original flight, you will likely lose the supplemental UG fee that you paid. Fees for paid UGs are not refunded.
So, if the original flight is cancelled, you are out of luck..
It is better to have the ticket reissued as an actual FC ticket, rather than risk having a ticket that is a coach ticket with a paid UG.
If I want to fly FC, and the incremental fare is not outrageous, I'll purchase the coach ticket (so that I have a record of what to invoice my client), then call DL and ask them to cancel the coach ticket and sell me the FC ticket.
That process was easier before DL told us all to go pound sand when they changed the customer support call system.
This depends on the airline and has not been an issue on DL recently though I believe it may have been at one point.
Two examples from this year for me, one with DL and one with AA:
DL: I booked GSO-DTW-DAY in Main Cabin. Sometime after booking, I upgraded the GSO-DTW leg via a buy-up offer in the App which I used miles to pay with. Fast forward to the day of the flight, I receive a notice in the morning my GSO-DTW leg is delayed significantly. Options out of GSO were full or got in way too late. App allowed me to rebook out of RDU and I was able to rebook into F on both RDU-ATL and ATL-DAY, even though I was technically only in F on one-leg (GSO-DTW). For DTW-DAY, I was in Main Cabin. But the App let me rebook to an option that gave me F on both legs. Some options only had F available on RDU-ATL or ATL-DAY if F was full on one of those legs but I found an option with seats open on both legs that was also the best option for timing anyway).
Also, when I've rebooked a new flight on DL, even after buying up with the App, the full amount I've paid (original Y fare plus the fare for the buy-up) was applied in the e-credit towards the new flight.
AA: It did not work the same way as DL. I booked DAY-DFW one-way in Main Cabin. A few days later I bought up to FC via an Instant Upgrade buy-up offer in the Manage Trips section. A few days after that, I realized my schedule would permit me to leave earlier than I initially thought and the FC fare on the earlier DAY-DFW flight was within a few bucks of my AA Main Cabin Fare plus the buy-up offer on the flight I booked. I called AA to try to move to the earlier DAY-DFW flight, hoping to book into FC with the main cabin fare I paid plus the upgrade fee I paid. The agent told me that the only portion of the fare that would apply towards the new flight if I wanted to switch was the Main Cabin portion of the fare, and that the money I paid for the instant upgrade would just be lost if I switched my flight. I ended up not switching.
ETA: Not sure how it works on UA, though one issue on UA others should be aware of is although change fees are waived, if you change flights within the trip and the new flight is cheaper, you do not get the difference back as an e-credit (you do on DL). It's just simply treated as an even exchange. I do not know with UA if you cancel the ticket completely and get an e-credit if the e-credit retains any residual value that way or not or if you use a $500 e-credit for a $400 flight, you're just still out on that $100.