Originally Posted by jeffreyt
If that were true, then they would never sell any F or J seats that they do, because people would just buy "M" fares and be automatically upgraded.
As I understand the complex DL SM's rules, only PM's are upgraded at time of booking on YBM fares. If DL could convince it's PM's to buy only YBM fares, they could probably forget about Chapter 11. These fares are usually double or triple the LUT fares.