Air Transport Services Group (ATSG), which handles cargo for Amazon and DHL, said the companies are cutting back on flights in response to lower customer demand. 

"Both companies are adjusting their ground and air distribution and fulfillment networks in the United States to conform to reduced U.S. economic growth and consumer spending levels in the first half of 2023," the company said in a news release. 

ATSG said the 767 freighters dedicated to those customers will see reduced schedules and fewer block hours per aircraft in 2023 compared to last year. 

This tracks with recent data from the International Air Transport Association, which found that global demand for cargo was down 13.7 percent year-over-year in November.

“Air cargo performance softened in November, the traditional peak season," said Willie Walsh, director of IATA. "Resilience in the face of economic uncertainties is demonstrated with demand being relatively stable on a month-to-month basis. But market signals are mixed."

Amazon notably just reported one of its worst-ever quarters. The company has announced plans to cut 18,000 jobs and hit the brakes on its ongoing build-out of warehouses.