Etiquette for apologizing

Hello. I manufacture handmade garden urns and statuary in the U.S. Recently, we had a large order that was shipped to Macau and will be installed at a new casino in Macau. We pride ourselves on shipping our orders on the day that we promised, but we shipped this order a little over four weeks late. The customer wanted the order to be delivered directly to the casino, as opposed to the port. This proved difficult, as most freight companies would only deliver the order to a sea port. I'd like to know the etiquette for apologizing and taking responsibility for the delay. Many thanks for your help.