Originally Posted by
dddc
Can I make it a Y shorthaul and then still use avios with the future travel voucher to book J and go longhaul? (using avios to pay the difference, plus taxes of course)?
book whatever you want in terms of route and cabin for the one you intend to cancel. when you come to make a new booking with the FTV you will just add in the extra avios and taxes/fees/charges at that stage.