Originally Posted by
Lux Flyer
Using miles to cover the upgrade has been around for at least a few years as well. I believe the only thing they changed recently was making it available via mobile, in addition to a PC. IIRC in 2017 I did it on a PC booking.after I bought my coach ticket in cash, then paid the upgrade cost with miles. Also believe it used to require certain economy fare classes to be eligible to use the miles for an upgrade, so I don't think V/X buckets would qualify, which is why people don't always see the option; maybe they changed that too?
Did you pay for upgrade with miles online, or did you have to call an agent to perform upgrade? They previously allowed you to upgrade online at time of purchase, but not post purchase. For that you had to call in and request a mileage upgrade award which depended on availability and only certain fare classes were eligible (T or higher for domestic). The ability to pay for FCM offers with miles post-purchase was only added in 2018 and the ability to do it on the mobile app was recently added. They changed the FCM system back in May of 2017. Previously, I would rarely see offers on X/V fares. Now I see them consistently on all flights (including X/V) and the FCM offers no longer appear to vary with original fare class. I've seen the exact same offer for both a revenue ticket and award ticket on the exact same flight. The only time I see them go away seems to be when the number of seats left in the FC buckets drop below a certain threshold (typically 3 or less). I suspect they want set aside a certain number of seats for last minute purchases rather than offering all of them as upgrades.