Originally Posted by
ISTFlyer
It is possible to upgrade them via miles or cash.
If you want to purchase a cash upgrade -> Log in through MMB on LH.com. If a cash upgrade is offered for your flight, it would appear on the reservation page.
If you want to upgrade with miles via Miles&More -> You could upgrade the flight in most of the paid Economy fare classes, however, Y and B would cost fewer miles.
If you want to upgrade with miles via another partner program -> You should be able to upgrade Y and B fare classes only, however, some FFP may have exceptions that you could upgrade cheaper fare buckets.
Okay, flight is purchased through United on Lufthansa metal. Called Lufthansa and was told it isn't possible to upgrade. Thoughts?