That marks about an 8 percent on-month drop from February, when the tally came to 24 routes with 1,363 flights, and has little changed from a year earlier, it said.

"It seems that the Chinese authorities have made up their mind not to allow any additional flights or new routes to and from Korea," an industry official said. Local airlines said their China-bound scheduled flights will operate as usual.

On Wednesday alone, the number of Chinese group tourists who arrived in Jeju stood at 1,913, down 21.8 percent from a year ago, the KAC said.

Given that air carriers tend to expand scheduled flights every year, the drop in the Jeju-China routes is regarded as one of the latest cases in which Korean businesses are being hurt by China's response to Seoul's stationing of the Terminal High Altitude Area Defense.

The decision led by South Korea and the US has angered Seoul's biggest trading partner, who claimed that the anti-missile system will be used to spy on its own military. The two allies have repeatedly said it is aimed at deterring the nuclear and missile threats from North Korea.

Despite such justification, China has intensified its retaliation against South Korea, imposing restrictions affecting travel, hospitality and retail industries.

Shanghai-based Juneyao Airlines reduced its Shanghai-bound flights from Jeju to twice from nine times a week, and put its Ningbo and Hangzhou-bound routes on halt.

The Shenzhen-Jeju route offered by China Southern Airlines will stop running from April, which comes months in advance as the halt was initially planned for October.

About 114,493 tourists who had been planning group tours to Jeju via nonstop flights have canceled their trips so far this year, according to the Jeju provincial government. Some 1.2 million Chinese tourists visited the island last year on package tours. (Yonhap)