In the EU since 2005,[4] as of 2021[update], Regulation 261/2004 requires airlines to first appeal for passengers to voluntarily release their seat,[4] maybe by giving an offer of compensation but its amount is not regulated. If volunteers are insufficient, airlines will then refuse some passengers the right to board, in which case Regulation 261/2004 sets out compensation requirements for airlines that deny boarding to passengers due to overbooking.[4][5] Regulation 261/2004 does not mention the fate of passengers who failed to reconfirm and have been denied boarding.[4]