It’s not a massive new headquarters, but Amazon has been building up a little-­known facility it has in Hawaii.

The online retail giant established a package receiving and distribution facility at the Daniel K. Inouye International Airport nearly a year ago after deciding to fly its own cargo planes to Hono­lulu from Riverside, Calif. It began in April with one flight per week and then expanded to two per week in July. And in November, the Amazon Air flights were increased to daily arrivals. Astute local Amazon customers have been noticing faster deliveries, and it’s because of the dedicated flights and package facility that the company had not publicly announced.

Rena Lunak, a spokeswoman for Amazon’s air cargo network, said the Hawaii facility is part of an air service operation the company began three years ago. The initial purpose of starting Amazon Air was to accommodate the flood of holiday-season packages that overwhelmed carriers such as UPS and FedEx. Then the focus became using the new flight service to reduce transportation costs and speed up deliveries.

Shipping times to Hawaii from the mainland are considerably longer than within the continental United States, so setting up what Amazon calls an “air gateway” in Honolulu made sense.

“The idea was let’s find a way to fly to Hawaii, and that way we can get packages to customers faster,” Lunak said.

The service using planes branded with “Prime Air” lettering has shaved two to seven days off common Amazon delivery times to Hawaii customers — going from between five and 10 days to three days in many cases, according to Jacob Amsbaugh, an Amazon gateway process engineer who was in Honolulu Thursday. Amsbaugh said a goal remains to provide two-day shipping to Hawaii.

“We want to ultimately fulfill the two-day promise,” he said.

Amazon’s daily flight can carry up to about 20,000 packages, which represents only part of the company’s package volume to the state. Other partners such as UPS, FedEx, the United States Postal Service and Aloha Air Cargo still fly Amazon packages to Hawaii and deliver them to customers.

At Amazon’s Honolulu gateway, packages already bundled by destination ZIP code are taken off the plane in bulk and then loaded into containers destined for individual post offices by truck.

The air gateway is Amazon’s only operating presence in Hawaii, and is run by Pacific Air Cargo with a staff of more than 20. Pacific Air handles cargo for a variety of customers including commercial airlines.

“This is a good addition for us,” said Thomas Ingram, Pacific Air chief operating officer. “(Amazon) is a good customer.”

Amazon established its own air cargo network in 2016 by agreeing to lease 40 Boeing 767 planes from Air Transport Services Group and Atlas Air over two years. In December, Amazon announced plans to add another 10 planes to its leased fleet of cargo planes over the next two years.

To handle Amazon Air cargo, the company has established about 20 facilities at airports around the country, including delivery gateways like the Honolulu operation as well as much larger regional distribution hubs. Plans exist to build more of these facilities to support Amazon Air growth, including a $1.5 billion hub at the Cincinnati/Northern Kentucky Airport expected to open in 2021. This project on 900 acres is expected to employ more than 2,000 people with room to accommodate more than 100 planes.

Amsbaugh said he expects that Amazon Air serv­ice will expand further in Hawaii as the retailer, which likes to say it offers earth’s biggest selection, grows. “There’s a lot of demand here, and Amazon Air is still relatively new,” he said.