(CNN) - A U.S. senator from Connecticut is calling on major shipping companies to refund customers whose packages didn't arrive in time for Christmas as promised.
"I am disappointed to learn that so many consumers in Connecticut and across the country made purchases this holiday season expecting their gifts to arrive in time for Christmas, but instead were left empty-handed," Democratic Sen. Richard Blumenthal said in a statement.
Some UPS customers reported missed arrival dates, and FedEx was late with some deliveries as well, but those were "isolated incidents," the company said in a statement Thursday.
UPS said Friday that customers with air or international shipments are entitled to refunds, per UPS's service guarantee.
But that guarantee was suspended for shipments via ground transportation beginning December 10 as part of an industry standard, according to the company.
Blumenthal acknowledged that workers for UPS, as well as FedEx and the U.S. Postal Service, work "grueling, long hours" during the holiday season.
"It is incumbent upon these companies, however, that when a customer is quoted a delivery date ahead of Christmas, gifts arrive on time," he continued. "In a very real sense, Christmas is on the line. I call on UPS to do the right thing and provide refunds to people whose Christmases were a little less cheery as a result of their late deliveries."
Both UPS and FedEx noted they were handling hundreds of millions of shipments in a compressed holiday shopping time frame, because Thanksgiving was later than usual this year.
A spokeswoman for UPS also said the company was dealing with a backlog from previous severe weather in the Dallas area.
- CNN's Ashley Killough, Kevin Bohn, Josh Levs, Ashley Corum and Nick Valencia contributed to this report.