Thank you much for the info. Since moving to DC I have been been able to avoid LH across the Atlantic. In BOS LH was the only way to go BOS-FRA.

So can you hypothetically acquire these LH vouchers ahead of time, i.e. without booking a flight, in case one needs to fly on short notice? Is the upgrade structure identical to UA flights (class UGable and miles)?

Re SK: the lack of integration btw SK and UA is apalling. I was in ARN and bought a full fare Y class ARN-IAD via CDG. On the UA leg the SK ticketing people could neither put me in E+ nor do an upgrade. They couldn't even get me a phone # for UA. Actually, they told me that E+ was full, which I knew was BS. So I had to get online and look up the Swedish toll free number for UA.

Note, that US appears to have some sort of pan European 800 number on the back of its card. Never knew that there was such a thing.