I believe it's possible, in the strictest definition of the word. I think a determined agent could get the record updated to show either an earlier fare break or -- what I was actually thinking -- to update the flown leg retroactively to W and price the thing. Keep in mind, SHARES does very little validation on its own -- it basically trusts the user to know the rules. But I agree that it's unrealistic, and that the three options you have listed here are the ones to plan for. Of the three, only the last could be done after departing SIN, and it would require R space that's currently available and a US$600 co-pay per person. There's also #4 , attempt to buy a TOD/HOD upgrade after check-in, but this probably won't be an option until the SIN-NRT coupon is lifted, as opposed to at T-24.