I am not sure if this has been answered before... but when I hold DONEx ticket and one of the flight is sold-out in "D" class with "E (Premium Economy)" available? For example, I am looking at NRT-DEL and on most of Sundays, which I need to fly is sold out in D so I cannot book that flight unless I downgrade myself to lower class. The next class of service is premium economy. Would they allow me to travel in PY on a DONx ticket or will they make me fly in Y?