Originally Posted by
irishguy28
It does not matter whether you're booked under the operating airline's flightcode or any codeshare partner's flightcode; all that matters is the identity of the operating airline. In this case, Delta is a non-community carrier, and that remains the case even if booked under a KL- or AF- flight code.
That's actually not correct.
The following case established that a community carrier (KLM) is liable for EC261 on their codeshares where the non-community carrier's flight (on Delta metal) impacts a connecting flight operated by a community carrier:
Case C-367/20 KLM Royal Dutch Airlines
http://curia.europa.eu/juris/liste.j...C-367/20&jur=C
So, if someone flew a ticket from JFK to FRA via AMS with the first leg being a KLM codeshare on Delta metal & the second being on KLM metal, a technical fault on the former that impacted the latter flight would be EC261 eligible.
That said, there's obviously no right to compensation on flights diverted due to weather; however, there is a duty of care.