Recently the ATC personnel in France has been on strike. I was supposed to fly from Lisbon to Zurich, with the last flight of the day (Zurich airport closes at midnight or so).
Due to the accumulated delays during the day, due to the strike, our aircraft arrived late and we never got the permission to start, so the flight was cancelled after we had already boarded. They rebooked me on the same flight the next day, where exactly the same thing happened again. (After that they booked me on the first flight in the morning the next day which was only shortly delayed).
My question is: How directly must an airline be affected by a strike to be ineligible to pay the compensation according to EU Flight Compensation Regulation 261/2004?
It does not sound like an unplannable thing to me, especially since it happened two days in a row (there were some there who claimed this was the fourth time their flight was cancelled, in a row). The strike was even announced more than 14 days in advance (see first link). Also, the airline servicing the flight is not the one whose personnel is actually on strike.