Originally Posted by CaptainMiles

Booked LIS-EWR-ATL on one through ticket.

Original booking:
LIS-EWR TP201 scheduled 11:20-14:30
EWR-ATL UA1245 scheduled 17:11-19:45

Minimum connecting time for TP-UA at EWR is 1h25m, and this was booked with 2h41m connecting time.

TP delayed, arriving EWR at 15:53. As a result, MCT was blown, and indeed pax arrived at the UA1245 gate at 17:07 just as they had closed the doors. UA1245 departed on time. Pax rebooked onto the next UA flight, UA607, scheduled 21:10 to arrive 23:44. Interestingly, per the schedule this would result in a 3h59m late arrival, just one minute short of any compensation due.

However, UA607 delayed, a little bit at a time. 22:40, 23:00, 00:12, 01:00, 01:20, 03:00, 06:00, currently estimating departure 06:15 next day, and who knows if there will be further delays.

It would appear that pax is due 600 EUR compensation due to arriving > 4 hours late. Question is: which airline is liable? TP was to blame for missing the original EWR-ATL flight, which started the whole thing. But UA was the one that caused the delay to exceed four hours. I can just see that both would deny the claim: TP saying that their delay would cause a delay of 3h59m, which does not get compensation; and UA saying the delay is a domestic US one, not covered by EC261, and it was not the originally ticketed flight that delayed.

Any advise on who to claim against? Or is this so complicated that it is best handled by one of the EU-based EC261 claims specialists companies? Or no hope of collecting from either airline?