Originally Posted by LTN Phobia

I believe it's the operating carrier that grants the ORC rather than a ticketing carrier? (Particularly if it was booked under the AY flight number rather than under the BA flight number.)

As for EU compensation, it is entirely on the operating carrier and ticketing carrier is not of relevance, I believe.

Another thing is that AY was not at fault here, the issue was with AA, so I suspect AY may be rather reluctant to help.