Korea's first polyester fiber on company grounds. It established Sunkyong Fibers Ltd. in July 1969, and started to produce original yarn. In 1973, SK then established Sunkyong Oil, beginning a vertical integration strategy to manage production, "From Petroleum to Fibers". That same year, the company acquired the Walkerhill Hotel.

In 1976, Sunkyong Corporation received an international trading company license from the Indian government. In December 1980 SK purchased privately run Korea National Oil, making