AC*SE: Your analysis is correct, but in practice, how often is AC in position when they have to turn revenue J pax away because there are no seats left in J. My recent experience is that the only time J is full is when AC crew are travelling. The PTO maos the day before the flights typically show low loads, which then fill up at flight time. I suspect that they lose very little business as a consequence of time of booking upgrades. I'd like to see the data.