If the overall weight of your luggage exceeds your baggage allowance, excess baggage fees will apply. It is important that the airline is notified up front of any baggage in excess of passenger’s allowance. We reserve the right to refuse the carriage of baggage that exceeds the allowance on the same flight as the passenger. Overweight bags can only be paid for at airport check-in.You can purchase extra bags online (20% discount), at the Icelandair Service Center (20% discount) or when you check-in at the airport.
or more details visit : http://www.icelandair.us/Baggage/Baggage-Information