COLORADO SPRINGS, Colo. -

Shoppers swapped out unwanted Christmas surprises Thursday while others were still waiting for those surprises to arrive.

UPS and FedEx missed the holiday deadline they promised customers. People in southern Colorado and across the U.S. were still expecting presents in the mail Thursday, too late for Christmas.

UPS and FedEx would not say the exact number of packages that didn't make the holiday deadline. Jennifer Lesh can count at least one.

"I bought a special book for my dad that's actually out of print and it didn't arrive on time," said Lesh.

Matt VanAuken said it was a similar story for his family across the country.

"We had a lot of family in Texas and in California that didn't get what they needed and were guaranteed shipping and still didn't get it, so they were pretty upset," said VanAuken.

The shipping giants offered these reasons for this holiday season's shipping fiasco:

  • Icy weather slowed air travel in parts of the country.
  • Incorrect projections about the volume of this year's business.
  • More options online increased shipping demand.

UPS CEO Kurt Kuehn told CNBC earlier this month the company did not increase the number of seasonal workers for this year.

"We continue to become more efficient and use equipment on the ground for routing and scheduling, so we can meet increased demand with a pretty much fixed amount of resources," said Kuehn.

Thousands of customers have voiced their complaints about the shipping companies on social media sites like Facebook and Twitter using hashtags like "#UPSfail" and "#FedExfail."

"My dad was understanding so it's OK," said Lesh.

Lesh said she isn't disappointed about the late delivery. Instead, she sees it as an opportunity to celebrate again with her father when his book does arrive.

UPS is taking most of the criticism because it partnered with the popular website Amazon. Amazon has pledged to refund shipping costs and provide $20 gift cards for shoppers who were affected.  It also said it will evaluate its UPS's holiday performance.