In my case, I filed a complaint with Iceland air regulatory authority, even though
I lived in canada at a time, and when I told Icelandair I had done that, they suddenly became very proactive.
There are also firms that handle all of this for you for a % (in the region of 20%). They validate the claim and threaten ti take the airline to court if they don’t pay out.
I generally go direct to the airline these days but if I get pushback beyond what I’m willing to deal with myself, I’ll use one of those services.
Very common in Germany. Non-existant in Finland. Finnish consumer rights are very weak, they only work if the business cooperates[1]. Finnair is a state-owned company that acts like if they were legislation and courts themselves. I have avoided them as much as I can for many years.
[1] Probably the majority of businesses does. But shady used car dealers etc. and Finnair don't.
