Delta Air Lines (DL, Atlanta Hartsfield Jackson) has increased its stake in Korean Air (KE, Seoul Incheon) holding company Hanjin-KAL from 4.3% to 5.13%, it announced in a report to the South Korean securities exchange.

The move builds on a pledge revealed by the US carrier in June, when it made the surprise purchase of the 4.3% shareholding, that it would eventually raise its stake to 10%.

Hanjin-KAL owns a 29.9% stake in Korean Air, which like Delta is a Skyteam member. Most of the remaining shares are held by investment and pension funds.

"The purpose of the investment is not aimed at affecting the management rights," Delta said in its report.

In a letter sent to Delta in July, the Korea Corporate Governance Improvement (KCGI) hedge fund - which owns a 16% stake in Hanjin-KAL - asked it to clarify the purpose of its investment, according to South Korea's Yonhap news agency.

This was because the unexpected move had helped to clear uncertainties surrounding Hanjin-KAL's struggle to defend its management rights against attacks by hedge funds such as KCGI. In April, the Hanjin board had named the son of the late chairman Cho Yang-ho, Won-tae, as the new chairman, and KCGI had demanded that a court appoint an auditor to review this appointment process.

However, Delta insisted in its reply to the hedge fund that its purchase was not a ploy to interfere in Hanjin-KAL's management rights but was part of its investment plan.