Delta Air Lines Inc. bought a stake in the parent of its joint-venture partner Korean Air Lines Co., deepening a push into Asia and bolstering the controlling family in its face-off with activist investors.

The Atlanta-based airline acquired 4.3% of Hanjin Kal Corp., Korean Air’s largest shareholder, and expects to boost the holding to 10% over time, subject to regulatory approval. The cost of the investment, announced Thursday, wasn’t disclosed.

The deal is a boost for Walter Cho, the new chairman of Hanjin Group, who’s seeking to consolidate his control of the airlines-to-logistics empire after his father’s demise in April. Among Cho’s challenges are activist investors including Korea Corporate Governance Improvement fund, who have been demanding transparency and better returns.

“The Cho family and KCGI are in a race ahead of the next shareholders’ meeting in March,” Lee Sang-hun, analyst at HI Investment & Securities Co. in Seoul. “Considering their strategic alliance, I can assume Delta could be favorable to Cho family.”

Delta’s Commitment

In a statement, Delta said its investment “reflects our commitment to the success of the joint venture” but the airline declined to comment on other Hanjin Kal shareholders.

KCGI, which has increased its stake in Hanjin Kal to almost 16% over the past few months, has been pushing for changes at the holding company including reductions to directors’ pay. Showcasing their power, shareholders backed by activist funds in March voted to remove then-chairman Cho Yang-ho from Korean Air’s board, just days before he died.

An inheritance tax, among the highest in the developed world, stands in the way of the junior Cho’s efforts to get hold of the late patriarch’s almost 18% stake in Hanjin Kal, which is crucial to tightening his grip.

Hanjin Kal’s shares fell as much as 12%, the biggest intraday drop since August 2015, on Friday in Seoul, signaling investors now consider the activists’ bid for control is less likely to succeed. Korean Air, in which Hanjin Kal owns about 30% stake, dropped as much as 3.4%.

Delta’s acquisition also comes about a year after the two carriers began a trans-Pacific venture that allows them to coordinate flights in Asia and in the U.S.

The agreement is part of Delta’s strategy to expand outside the mature U.S. market by taking minority stakes in other carriers, particularly in emerging markets. Delta already owns shares in China Eastern Airlines Corp., Grupo Aeromexico SAB and Brazil’s Gol Linhas Aereas Inteligentes SA.

“This is already one of our fastest-integrating and most successful partnerships, and experience tells us this investment will further strengthen our relationship,” Delta Chief Executive Officer Ed Bastian said in a statement.

The Korean Air partnership is contributing to Delta’s first growth in the Asia-Pacific region since 2012, the U.S. carrier said. The airlines also cooperate in air cargo.