Originally Posted by
PiperAtGatesofDawn
UK's J cabin is always at a premium for cash or miles and I believe the upgrade system is quite broken.
However this miles upgrade in this case seems to be a need trick to save miles (I assume you can upgrade a miles ticket). So in the case of DEL-BLR an outright J ticket costs 28k miles. And a Y ticket costs 7.5k miles + J upgrade costs 14.5k miles. Thus saving you 6k miles!

If all goes to plan...
What's the cancellation fee/penalty, if any - for a mileage ticket on UK?