Given the current crisis, I'd guess one can reasonably say that 5.3
An operating air carrier shall not be obliged to pay compensation in accordance with Article 7, if it can prove that the cancellation is caused by extraordinary circumstances which could not have been avoided even if all reasonable measures had been taken.
is indeed relevant. As such cancellations would not anymore give a right to any compensation. But what about refunds (which are, for obvious reasons, made difficult by many carriers) ? I don't see a "force majeure" clause in the regulation.
Thoughts ?