HONG KONG—Chinese authorities have detained a FedEx Corp. pilot in the southern city of Guangzhou, elevating pressure on the express shipping giant that is already in Beijing’s crosshairs amid a U.S.-China trade war.

The pilot, a former U.S. Air Force colonel named Todd A. Hohn, was detained a week ago while waiting for a commercial flight to his home in Hong Kong after flying deliveries throughout Asia from the FedEx regional hub in Guangzhou, people familiar with the matter said.

A lawyer for the Hohn family in Niceville, Fla., confirmed that Mr. Hohn had been detained in China. He was a wing commander at the Altus Air Force Base in Oklahoma until 2017.

Reached briefly at his hotel room Thursday, Mr. Hohn identified himself to a reporter and then referred all questions to a family lawyer and discontinued the phone call. He is married and a father, the people familiar with the matter said.

When he was detained, Mr. Hohn was carrying nonmetallic pellets used in low-power replica air guns in a checked bag, the people said. Chinese authorities have alleged that Mr. Hohn was illegally transporting ammunition and have begun a criminal investigation, the people said.