Yeah I know about that fare basis chart, but as D class is basically just discounted business class domestically and the P class fares on the same route are the same price that D class would have a similiar restriction.

So if you really want to travel on a discounted domestic ticket, you should look for D fares rather than P if possible so that you aren't downgraded to Y if there is an aircraft change? What if the plane changes and the cabin is now regarded as first class instead of "business elite" will I then be put into economy or placed in the first class section. (We all know its the same cabin, but the seating chart does change when you on a D ticket compared to P)

I called Delta and their Filipino call centre was very unhelpful. The agent was really brisk, unhelpful and unapologetic. They basically stated that they don't offer credit towards other flights if pricing changes (unlike United used to do for me) and that if I wanted a refund I'd have to wait up to 2 months to have it processed. Not impressed with Delta at all.

Updated: YA00UPNQ is the fare basis code so it is indeed a "up" fare.