i miss flying them. delta used to sell those CI operated under DL codeshare flight numbers. i managed to get one last time back in february, but they are no longer available. the prices were very competitive. i remember paying roughly 3K for business class, and the change fees were like $80. i was able to earn the full MQMs and MQDs based on delta's earning. i really enjoyed their service, food and seat comfort. hopefully delta will put those codeshare flights back in the system again.