Here's a very long winded posting from the United forum regarding exactly the same situation. The secret is the Wegner Decision that covers connection flights. https://www.bottonline.co.uk/blog/co...-now-claimable

Success!!!! with Air Canada, not with UA but maybe instructive anywayQuote:
Originally Posted by hughw
This may be a bridge to far for some of us, but I've found forms online where you can take a complaint directly to the national authorities from where the flight originated if you're not satisfied with the airline's response.

Here's the general English complaint form...https://ec.europa.eu/transport/sites...nt_form_en.pdf

Here's the addresses for all the national authorities... https://ec.europa.eu/transport/sites...ent_bodies.pdf

And in my case, leaving from France, here's the form in French from the French authorities. you need to download the PDF by clicking the appropriate place on the top of the form
https://www.formulaires.modernisatio...numCerfa=13675

I'm not sure in what way this helps resolve with the airline. The form actually states "Please note that the competent authorities of Member States cannot in general take binding decisions on airlines in respect of individual complaints. If you are still not satisfied with the airline's response, even following the answer from the competent authority, you will have to pursue the matter in Court or through alternative dispute resolution." But I would guess that it does put some additional pressure on them to settle.
I made two ill-fated attempts to receive compensation for six family members who were delayed over 4 hours on their return trip to Boston from Bordeaux connecting in Montreal on Air Canada. Tickets were all mileage awards booked with UA miles. While the BOD-YUL flight was on time, the YUL-BOS segment was subject to the delay exceeding 4 hours. AC turned down my request curtly (saying their denial was final and not to bother contacting them again...that they considered the matter closed) with the explantation that since the flight segment was from a non-europeans community nation (Canada) to another non-community nation (U.S) that it wasn't subject to EU261.

I decided to make one last attempt and wrote an email directly to Twyla Robinson, AC's General Manager, Customer Relations & Executive Centre. I politely pointed out that I believed the prior denials of compensation were ill-informed and that the entire flight should be viewed as a single flight under the rulings of the European Court of Justice in the Wegener and the České/Etihad cases. I included pdf's of both those rulings in my email. At the end of my email, I said "In light of what seems to be the clear applicability of EU/EC 261, I would appreciate your review of our claim. We are hopeful that Air Canada will do what is right and and responsible. Failing a satisfactory response, it seems that we're left with little choice but to engage a third party to pursue the claim in the appropriate EU court and to file a report with DGAC Air Transport Directorate in Paris."

A week later, I received an email from a customer relations manager at AC stating "In this instance, we remain of the opinion that the compensation requested under EC Regulations does not apply. However, in the interest of concluding this amicably, on a goodwill basis, we will provide the compensation of 600 EUR per person. Converted to US Dollars at the current rate of exchange, the amount each person will receive is $662 USD. The compensation will be paid by bank draft (cheque). "

Naturally, I'm gratified that AC stepped up and did the right thing. I still don't know, and it doesn't really matter at this point, if their earlier denial was due to an ill-informed agent that thought the EX-YUL flight didn't count, or if it was AC policy to initially refuse in the hope that the claimant would go away, Obviously, by stating this was a "goodwill" gesture instead of compliance with EU261, they want to not set precedent for future claims. We're satisfied that the higher-ups at AC took the claim seriously and examined it on the merits.....and my family members (four of whom are college students) are delighted to each receive $662.00 USD checks which arrived yesterday, two weeks after the notification from AC.

Lessons learned:
1. polite persistence can pay off
2. knowing the facts and relevant regulations and laying them out clearly probably forced them into a position where they had to agree to compensation or look like fools
3. polite threat of 3rd party action in European Court of Justice and notification of relevant governing authorities perhaps helped.
4. going to higher-ups in the organization to someone who is in a position to make a difficult decision is sometimes necessary
5. delay to final destination, even if caused by connecting flight from a non-euro airport to another non-euro airport, counts as long as the overall flight from europe is a single booking.