Asking out of interest as much as anything. I booked a return ticket between BRU and SIN with Lufthansa in Premium Economy with the outbound travel on LH and inbound on SQ. The return flight was cancelled owing to last month's strike in Germany. After a great deal of effort, AMEX Travel booked me on an LX flight back to Brussels - but could only get me a seat in Economy.

I asked LH what their policy is regarding credit for not being able to travel in the cabin booked, only to get the answer "EU261 does not apply as SQ26 is operated by United".

I can understand that EU261 wouldn't apply to a flight operated by an non-EU carrier - in this case, SQ - not UA as stated by LH customer service - but it seems strange to essentially say "we don't care if you paid for more than you got". Is this normal?

It seems that you accepted a voluntary downgrade in order to get rebooked to the LX flight. Most likely you could have insisted to be rebooked into PE by waiting for a different/later flight with PE. Did you ask AMEX Travel to rebook you into a flight with PE available?

If SQ cancelled their flight it seems to have little to do with LH - LH issued the ticket? (it was on 220 ticket stock?)

SQ flights from SIN to Europe are not covered by EU Reg. 261/04. Neither LH or SQ is liable for the downgrade under EU Reg.

I would ask SQ for a refund for the downgrade on that sector. They should look at the historical fare for the calculation. I suspect it would be a few 100 euros.

SQ is not going to refund anything if this is a LH plated ticket. SQ will not get paid by LH for a flight where pax that has been rebooked to LX so there is no nothing to refund. Any refund will have to come from LH/whoever issued the ticket and collected the payment from the pax.

If SQ issued the ticket, then SQ is the obvious party to request a partial refund from.