Some useful links to the press release of the EUCJ and the ruling that states that ' a flight with one or more connections which was the subject of a single reservation constitutes a whole for the purposes of the right of passengers to compensation provided for by EU law. The applicability of the Regulation on Air Passenger Rights is to be assessed with regard to the place of the flight’s initial departure and the place of the final destination of that flight. A bit of a puzzle remains if I should address KLM (marketing carrier and responsible for the last leg) or the operating carrier (Delta who flew me on behalf of KLM from NYC=LHR). Since my current discussion is with KLM I will keep on playing it via them. My intention is to report back how this ended, but don't hold your breath - I expect a long back and forth game.
https://curia.europa.eu/jcms/upload/...cp220059en.pdf
https://curia.europa.eu/juris/docume...f?num=C-561/20