Delta Air Lines and Korean Air had a “troubled” partnership within SkyTeam for years until two airlines had a change of heart and decided to form a transpacific Joint Venture that has been now approved by both countries.
Delta members that credited Korean Air flights previously to SkyMiles program where in for a surprise because flights didn’t earn any Elite Qualifying Miles and award miles earnings were very low. Everything has changed effective May 1, 2018.
You can access Delta’s page for Korean Air here.
Here are Korean Air earning effective May 1, 2018:
Here are Korean Air earning until April 30, 2018:
Delta used to identify airlines on its website belonging to four different groups depending how close they were and the miles earnings were aligned accordingly. Korean Air used to belong to Group 4 airlines and you earned hardly anything.
Now, as a Group 1 airline, the earnings are much better. You have to bear in mind, however, that you don’t earn a lot miles if flying on discounted economy tickets.