Whether it is a volcano, tornado, electro-magnetic radiation, air traffic controllers' strike, "blind" bird or "blind" flock, or just a usual "bs" from the airline, the reason for your flight delay or cancelation could be interpreted by the respective airline as an "extraordinary circumstance." Why does it matter? It matters for you, as an air passenger, because in such circumstances the airline is not required to provide you with a compensation.
But, even in such unfortunate events, you air passenger rights are protected by the law.
Regulation EU 261 provides that passengers whose flights are canceled should be able either to obtain reimbursement of their tickets or to obtain re-routing under satisfactory conditions, and should be adequately cared for while awaiting a later flight. Accordingly, pursuant to Article 8 of Regulation EU 261 in case of flight cancelation an air passenger shall be offered by the operating airline:
1. Reimbursement within 7 days of the full cost of the ticket at the price at which it was bought, for the part or parts of the journey not made, and for the part or parts already made if the flight is no longer serving any purpose in relation to the passenger's original travel plan, together with, when relevant, a return flight to the first point of departure, at the earliest opportunity.
2. Re-routing, under comparable transport conditions, to their final destination at the earliest opportunity, or
3. Re-routing, under comparable transport conditions, to their final destination at a later date at the passenger's convenience, subject to availability of seats.
It is important to know your air passenger rights!