ORLANDO, Fla. -

Delivery trucks driving out of United Parcel Service's Orlando hub tried to make up for a backlog of deliveries on Thursday.

Thousands of customers throughout the nation report delays in receiving their holiday shipments, causing some of them to give I.O.Us instead of gifts.

Megan Bittakis of Orlando said she was waiting for a delivery from her brother across country.

"He said to expect my husband's and son's gifts on Tuesday, the day before Christmas," she said. "They did not arrive."

Local 6 watched as a UPS driver delivered the package on Thursday -- two days late.

Danny and Reeny Dawson had a similar experience.

They were waiting for a package that contained a gift for a house guest.

"I looked online, and it arrived in Orlando at 11:30 on the 24th," said Reeny. "(I thought) Well, clearly, we're not going to get it on the 24th."

UPS admitted on Thursday its workers were inundated by the large volume of shipments over the holiday and apologized to its customers.

On Twitter, the company assured them saying, "We experienced heavy volume and (we're) making every effort to get packages to their destination."

Some customers also complained Fed Ex had delayed their deliveries.

Fed Ex admitted to Local 6 they had a few delays, but denied there were any widespread problems.