I'm thinking of upgrading my AI economy ticket on DEL-NRT sector to business class availing "UFS" (Upgrade for Sure).

It's a bit confusing because there is another upgrade scheme called "Get Upfront Upgrades" and both of them can only be done if there is an empty seat available within 24hrs of departure. The difference according to AI site seems that UFS is actually re-issuing the ticket to the eligible business class RBD, where as the latter GUU only issues EMD hence the mileage earning is only possible for the original booked class. Funny enough, both charge the same amount, so it's much better to upgrade through UFS.

I'm thinking of doing this at the airport itself. Has anyone tried UFS before? Was it easy to get it done?