LOUISVILLE, Ky. (AP) — Tiera Washington’s workload doubled during the holiday rush at UPS’ largest air hub, where seemingly endless streams of packages are sorted and shipped as the peak season puts the package delivery company to the test.

The 23-year-old’s usual four-hour daily shift can stretch to seven or eight hours, and sometimes lasts 10 to 12 hours, as a small army feverishly plucks packages off a conveyor belt and loads them for air and ground travel in a cavernous building that would cover 90 football fields.

“We get to make Christmas better for our families,” she said during a break. “So we’re helping them (customers) and they’re helping us.”

UPS, the world’s largest shipping carrier, expects to deliver more than 120 million parcels around the world during the peak week leading up Christmas, up 6 percent from the 113 million shipped during the same period a year ago.

The Atlanta-based company expects the pace to reach its pinnacle Thursday, with close to 26 million packages reaching their destinations. That volume is up more than 60 percent from daily norms.

Rival FedEx Corp., based in Memphis, Tenn., shipped about 17 million packages on Dec. 12, the busiest day in company history, it said. That one-day volume was up 10 percent from last year’s busiest day, and doubled total shipments on an average night.

Shipping performance and forecasts from UPS and FedEx are closely watched because they tend to indicate how the broader economy is doing by shipping so many packages for consumers and businesses.

FedEx attributed its recent record day to steady growth in online commerce, spokeswoman Carla Boyd said. Since 2005, the company’s busiest-day volumes are up almost 75 percent.

UPS has declined to offer a full estimate for how many packages it will deliver between Thanksgiving and Christmas. Last year, the company said it shipped more than 440 million packages worldwide between the two holidays.

But UPS spokesman Norman Black said that “clearly our volume has grown compared to last year.”