Korean Air Lines Co., South Korea's flag carrier, said Thursday it will begin placing smaller jets on several Japanese routes this month amid escalating trade tensions with Japan. 

The move is part of Korean Air's extended efforts to respond to a fall in Japan-bound routes after the neighbor implemented tighter restrictions on exports of key materials to Korea, in apparent retaliation against a series of South Korean court rulings last year over Japan's wartime forced labor.

Japan is also set to expand the export curbs to other areas, further casting a cloud on Asia's fourth-largest economy. 

Since the July 4 implementation of the neighbor's export curbs, Japan-bound trips fell sharply, forcing Korean Air and other smaller airlines to reduce or suspend some routes to Japan.

On Monday, the national flag carrier said it will suspend three regular flights per week on the Busan-Sapporo route starting Sept. 3.

"Anti-Japan sentiment is on the rise in Korea following Japan's restrictions on exports of three high-tech materials used in chips and display panels. If trade tensions with Japan continue, the passenger division will likely report a fall in its bottom line," a Korean Air official said in a recent investment roadshow.

In additional countermeasures, Korean Air plans to begin gradually putting smaller jets on routes between Incheon and Japanese cities like Sapporo, Osaka, Fukuoka and Nagoya in mid-August, a company spokesman said.

Instead of the 291-seat B777-300ER, for instance, smaller planes like the 276-seat A330-200 and the 248-seat B777-200ER will start running on the routes to Sapporo and Osaka on Sept. 12, he said. (Yonhap)