South Korean Prime Minister Kim Hwang-sik expressed regret on Tuesday over Japan's boycott of a South Korean air carrier following its test flight near a set of disputed islets claimed by both countries. Japan's foreign ministry has instructed its officials not to fly with Korean Air for a month in protest against the demonstration flight last month by Korean Air's first Airbus A380 near the islets, known as Dokdo in South Korea and Takeshima in Japan. The islets in the East Sea lying halfway between South Korea and Japan has been a source of recurring diplomatic row between the two neighbors.