Delta had a major glitch where you couldn’t see any award availability on partner airlines on their website when searching one way. They’ve fixed that. But they’ve also done something much better.
They used to black out Korean Air award redemption for nearly one third of the year. They just updated their terms and conditions to fix that, breaking out the different regions of the world which are supposed to have different ‘high demand dates’ in Korean’s program. Now you can use your miles for travel on Korean Air much more freely!