Overbooking occurs when airlines have sold a great number of tickets than seats available on the aircraft and the passenger is denied boarding.
In this case the airline has an obligation to seek volunteers to surrender their reservation in exchange for a full refund of the ticket or alternative boarding on an alternative flight. In particular, in the case where volunteers choose boarding on an alternative flight they are still be entitled to meals and refreshments in a reasonable relation to the waiting time.
Also, they are entitled free of charge two telephone calls or messages via telex, fax or email.
The passenger, however, who is not going to voluntarily give up their reservation, is entitled in addition to those already provided for the volunteer to compensation.
The amount of which varies depending on the route: