taranty

As I suspect was fairly clear from the context, I meant extraordinary. Post now edited accordingly.

Well in isolation it isn't, we're talking weather leading to ATC imposed delays, not just weather on its own. As a matter of common sense I do tend to agree with you, it doesn't seem fair to passengers that there's a different outcome from the same underlying event once ATC get involved. As a matter of law though that's just the way it is based on what the regulation says. This was confirmed fairly recently by the Court of Appeal, google blanche v easyjet for details. This is a fairly good summary: https://www.outertemple.com/wp-conte...WY-summary.pdf, as is https://www.lexology.com/library/det...3-8abcd01b610d.

As per my earlier post, weather alone is not automatically extraordinary, but if the weather then leads ATC to issue instructions and obeying said instruction results in a delay it's covered under recital 15 rather than recital 14 and is automatically deemed to be an extraordinary event. The claimant in this case tried to run the same argument that you are, saying that the underlying cause of the ATC delay was thunderstorms, thunderstorms aren't extraordinary thus compensation should be paid. The Court was very clear that it doesn't matter what the cause is of the ATC instruction, if the delay is due to ATC then it's automatically extraordinary due to the clear wording of the regulation.

The "all reasonable measures" bit does still apply, but in this case I don't see an airline has any ability whatsoever to do anything about it. You're sat on the ground at Frankfurt and ATC tell you there's a 30 min delay to departure due to arrival rates at Heathrow. What's an airline meant to do about that?