Every time it has happened to me the airline paid out quickly without any fuss. Once with KLM the plane broke over Siberia, they flew back and put me on a flight the next day. I got my 600 eur compensation and also the cost of two train tickets for the extra trip between home/airport and they didn't even ask for receipts.
For the longest time Ryanair actually gave me more money than I spent with them on tickets.
For the longest time Ryanair actually gave me more money than I spent with them on tickets.