Amazon wants customers to know delays were not its fault (Twitter/@Waff48).

UPS cited a large volume of air packages overwhelming its system as the reason shoppers were unable to receive all their purchases by Christmas Day. 

Despite the delays, UPS chose not to make deliveries on Christmas Day and resumed service today, Dec. 26.

The company has since apologized for inconveniencing customers.

READ MORE: UPS Apologizes For Holiday Delivery Delays

Amazon made it clear UPS' failures were UPS' alone, and that the retailer's centers processed all orders before deadline. 

Still, in an effort to ease its customers' minds, the retailer decided to refund shipping fees. The additional gift cards were also an attempt to calm the disappointed crowd.

A spokeswoman for Amazon, Mary Osako, said the company will be evaluating the performance of UPS' delivery carriers.

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