Originally Posted by
WhiskeyBravo
It means that DL isn't selling anymore. They could have 20 seats left and set Y=0.
This often happens with TATL flights. The day before, they are at Y=5 and then the next morning, Y=0. It's not because they sold 5 more tickets, it's because they don't want to sell any more tickets (which is surely the result of more variables than I could list here). They decided the risk of over-booking is too high.
Excellent info! ^^^ Thank you!