Originally Posted by
CowGirlMoo
Thank you everyone for your responses. I am, however, just as confused as before whether I should file an EU261 claim with KLM (the codeshare airline with the cancelled flight that caused the 24 hour delay back to the US) or with Delta (where I purchased the roundtrip ticket: DTW - ATL - FCO to Europe all on Delta metal) and FLR - AMS - DTW back to the US ( FLR - AMS was supposed to be on KLM, eventually ended up being BLQ - AMS on KLM, then AMS - DTW on Delta,
File with KLM as it was the KLM flight that was delayed and caused issue. Only if KLM fails to handle properly (doubtful in this type of case) theb file with DL.