A UPS shipping center in San Francisco had people waiting in line before the doors opened because many of the Christmas Eve deliveries promised never made it - leaving customers like Erica Lewis fuming.
"At this point, I'm crying because my Christmas presents are in that package. So here I am Thursday morning the day after Christmas coming to get my packages," said Lewis.
UPS says they're working around the clock to resolve the issue; a distribution center in South San Francisco was buzzing with pre-dawn activity. But this morning, there were still many angry customers sounding off on social media.
"Wondering if I can get refund for overnight delivery paid on 12/19, didn't deliver by 12/24, kid getting late #Santa gift today! #UPSFAIL," said Ricky Hernandez, @RickyDH1.
"Thank you for making my son sad and @UPSHelp is no help. They are horrible -- never again will I trust you. #UPSFAIL," said Mary Mercedes, @Preciosa0713.
Not all shots were fired at UPS - FedEx took hits too. Dr. Marc Saulnier wrote: "Major Christmas fail by @FedEx! My guaranteed delivered by yesterday package still hasn't arrived! Thanks for ruining Christmas. #FEDEX.
Still, some blamed shoppers waiting until the 11th hour to buy.
"If you wait until the last minute to buy your gifts, you run the risk of not receiving your gifts on time. It happens," said Jess, @JessOfRVA.
UPS and FedEx say there were too many last-minute air packages right before Christmas for them to handle. Both companies are also blaming bad weather for some of the backup. A spokesperson for UPS cited a backlog created by snow and ice in the Midwest last week - and an ice storm that hit Dallas two-and-half weeks ago.
FedEx said they will continue to work directly with customers to address any isolated incidents. In the meantime, additional workers were called in and UPS rented extra outside trucks.
Amazon, for their part, is trying to make up for the mess. They're emailing customers who were affected and offering to refund shipping costs and provide a $20 gift card.
"You know what, I'm no longer using UPS for my business or personal use at all," said Lewis.
UPS released this statement today: "UPS apologizes to both shipping and receiving customers who may have delays. We had additional sorting operations at Worldport, the UPS international air hub in Louisville, KY, on Christmas and are making deliveries and pickups today. Customers should continue to access UPS.com for the most updated information."
UPS and FedEx said they're expecting the bulk of consumer packages to arrive at homes today and tomorrow.