Schedules do not go without problems. There are shortages, late shipments, vendor delays, wrong products shipped, many employees home with the flu, etc. When a shipment to the customer is going to be late, he is to notified immediately so there is no surprise. Be prepared to give the customer a new time of arrival and ask him if there is anything else you can do to remedy the problem. He may have options. Make sure you stay in touch with him directly until the replacement shipment arrives at his facility. Be prepared to pay late fees if they were negotiated in the contract. If the customer has reacted favorably, you might consider covering the freight versus billing him, giving him some additional product at no charge or something of value to apologize for the delay.