Delta Air Lines said it has struck a partnership for a joint venture with Korean Air.

A joint venture immune to antitrust regulations would allow the two airlines to share costs and revenues on flights and coordinate schedules. The deal is subject to regulatory approval.

Delta and Korean Air also plan to offer more frequent flier benefits between their programs, expand “codesharing” to market flights and grow in the trans-Pacific market.

Delta CEO Ed Bastian said the newly-signed memorandum of understanding to implement a joint venture “deepens our longstanding partnership with Korean Air,” according to a written statement.

Delta and Korean Air have long been partners, and were founding members of the SkyTeam airline alliance in 2000.

But a joint venture is a closer partnership, and marks a rekindling of a relationship between the two airlines that had been more difficult in past years.

The move comes as Delta shrinks its Asian hub at Tokyo Narita airport, and seeks other ways to compete with United's and American's Asian networks.

Delta already has joint ventures with Air France-KLM-Alitalia, Virgin Atlantic and Virgin Australia, and recently struck a joint venture deal with Aeromexico.

Delta and Korean AIr had already announced plans for Delta to start Atlanta-Seoul flights in June 2017, adding to Korean Air’s service on the route.