Originally Posted by revigik

United Global Premier Upgrades are meant for United flights when you book a W fare or higher. They can be used on Lufthansa, what you have to do is call UA and ask for a paper certificate for use on Lufthansa; they will debit the GPU and mail you a certificate that you can use day of departure at the airport for your Lufthansa flight. This is only for Lufthansa. Regional premier upgrades are usable for United only domestically.