This is the biggest transit-time improvement effort since 1998, when UPS became the first carrier to offer money-back guarantees on its ground service. Each modification has knocked a full day off the previous guaranteed delivery time without affecting customer rates or pick-up and delivery hours.

Shipments between LA and New York are now guaranteed to arrive in four business days instead of five. Packages from Dallas or Houston to Florida now take three days, and from St. Louis or Kansas City to North and South Carolina two days.

Approximately 60 major origin/destination lane combinations were affected, including some of the nation's largest metropolitan population centers like Atlanta, Baltimore, Boston, Dallas, Houston, Indianapolis, Kansas City, Los Angeles, Miami, Minneapolis, New York, Philadelphia, Pittsburgh, San Francisco and Washington, D.C.

The improvements were made through changes in railroad service, modifications to UPS's hub-and-spoke interstate trucking network, and the recently deployed package flow technologies to speed up sorting operations inside package centers.

"UPS operates the most extensive and reliable ground transportation network in the nation, but we're always searching for more efficient ways to deliver for our customers," said Chris Mahoney, senior vice president, Transportation. "That effort is enabled by the technology we've deployed in recent years. It's the technology that allows us to search for new approaches to speeding the flow of goods for our customers."