Originally Posted by peter42
In my experience UA is at most airports (except LHR) not to sticky about upgradeable classes, but sure give it a try at the check in, lounge and gate.
just wanted to let you know they were VERY sticky with thr rules, no way of getting the upgrade by using the vouchers...so they will probably expire worthless as they are not valid for upgrading Biz Z Class either...thanks Star Alliance for these useful vouchers :-)