In case passengers are denied boarding, airlines are obliged to search for volunteers to give up their seats voluntarily in exchange for compensation. In addition, the air carrier must also offer volunteers the choice between a full refund and re-routing. You may be entitled to compensation of from €125 to €600 depending on the distance of the flight and the total time delay at the final destination.
Where volunteers choose re-routing, the airline must also provide assistance if necessary (food, refreshments, means of communication, etc.) and transportation between the airport and the place of accommodation.