UPS Inc. said today that it completed the second phase of a fairly ambitious project to expedite next-day air deliveries to more than 30 percent of the nation's 43,000 or so ZIP codes.

Under the two-step plan, 12,680 ZIP codes, most of them in areas away from major urban and suburban regions, will receive guaranteed small-package deliveries between noon and 2 p.m. Before last November, when the plan's first phase was rolled out, those ZIP codes only received next-day air deliveries at the end of the business day.

With the expansion, the service—which Atlanta-based UPS has rebranded as "Next Day Air Early" by dropping the reference to "A.M."—reaches 94 percent of U.S. ZIP codes and 98 percent of the nation's businesses, the company said. The service will also be available to UPS shippers in Canada, Mexico, and Europe, UPS said.

Most of the deliveries will be business-to-business (B2B), although the business-to-consumer, or B2C, market is not excluded, according to Peggy Gardner, a UPS spokeswoman.

Under the "Early" service that has been in effect for some time, UPS provides guaranteed next-day air deliveries between 8 and 8: 30 a.m. to businesses in closer-in, more densely populated areas.

UPS would not quantify the market opportunity that exists to justify what seems like a complex and demanding endeavor. "The market opportunity or demand is coming from both new and existing customers, so where we beat our competitors in terms of time-of-day commitment, the service will attract new interest," Gardner said in an e-mail. "And existing customers are using it because there was demand for the service."

Alan Gershenhorn, the company's executive vice president and chief commercial officer, said healthcare labs use the service to quickly receive specimens and expedite a patient's test results, while small, service-sensitive businesses like accounting firms would want to squeeze more hours out of a day to be more productive.