ATLANTA (AP) — FedEx, UPS and online retailers are working to avoid a repeat of the problems that occurred at the end of last year’s holiday shopping season, when severe winter weather and a surge in late orders from shoppers caused delivery delays.

UPS has spent $500 million this year upgrading its systems and processes and boosting the number of seasonal workers it’s hired. The company expects today to be its busiest day ever, delivering more than 34 million packages. As of midday, UPS says air and ground operations are operating smoothly.

In addition to adding 50,000 seasonal workers, FedEx invested in a new software system that helps supervisors anticipate fluctuations in package arrivals hours before an airplane carrying cargo lands.

Package carriers say they have been working closely with e-commerce retailers to help avoid problems as the retailers push shipping deadlines later and extend free shipping offers.

FedEx says so far, the planning has paid off.