in late 1998 there was a one time promotion for top-tier frequent fliers of all Star-carriers (6 carriers at that time only) giving them 'good at check-in-only' one-class/any-fare-upgrades good on any other Starcarrier (except the own one), they were very time limited (2 months?).
Flying TG it never hurts to ask how much a one-way-upgrade costs in $ (from ZRH to BKK TG offered during the whole last year, a one-way/one-class-confirmable upgrade good on any paid fare for only US$ 99!), that upgrade could only be purchased at TG's-downtown office in Zürich in person.