Amazon, for example, is investing nearly $1.5 billion in a new cargo hub at Cincinnati/Northern Kentucky International Airport, which is expected to open next year with a fleet of 70 planes. It will try to compete with UPS, which has more than 260 planes at its Worldport hub in Louisville, Ky., and with FedEx Express, which flies more than 650 planes from Memphis International and has been investing heavily there.

All the expansion means that “there’s more flight activity by smaller aircraft,” said Robert Mann, an industry analyst and consultant. “Cargo are logistics, so you want to use 24 hours a day if you can and because you can,” he added. Once a carrier has a hub and crew, he said, it can make more trips at lower cost.

While passenger airports are usually near population centers and leisure attractions, cargo carriers require proximity to warehouses, roads and rails. But cargo planes are increasingly flying out of geographically remote airports, Mr. Harteveldt said. And those secondary airports welcome the extra money that freight brings.

“Cargo shipments are a silent revenue driver,” said Atif Elkadi, the deputy executive director of Ontario International Airport, one of a constellation of airports in Southern California. Freight helped the airport weather the financial crisis more than a decade ago, when passenger traffic dropped over 45 percent.

Airports nearby noticed. In 2018, March Air Reserve Base received approval for Amazon Air to operate five cargo arrivals and departures a day; currently it runs three. Last year, the San Bernardino International Airport Authority Commission approved a new $200 million air cargo facility at that city’s airport. Officials estimate deliveries will add $5 million in annual revenue. Currently, there are 30 to 70 flights a week, depending on the season; it anticipates adding about 50 daily flights.

When the line between cargo and passenger facilities blurs, nearby residents like David Pearson feel the change.

Mr. Pearson lives in Idyllwild, Calif., which is within roughly 50 miles of the March base and the San Bernardino airport. He has lived with the noise from the sites for nearly two years, especially in the early morning and late at night. It was so bad, he said, he started tracking the flights. He said he had traced them to Los Angeles International Airport, about 100 miles away, and the Ontario airport. Ontario is a regional domestic hub for UPS, and FedEx and Amazon have operations there.