Originally Posted by
TTmex
When my friend worked in revenue management, he said that within the near year-long lifecycle of any flight (i.e. from when it's open to book until it flies), some flights on certain routes could be well over double booked, e.g. for Algeria they may at some point have had 350 people ticketed for 150 seats. The algo worked well and he said flights regularly went out full with barely anyone getting offloaded. With combinations of flexible tickets/date changes, no shows, misconnections, etc etc, they were remarkably good at working out how many tickets needed to be sold to maximize space onboard and thus revenue per seat.
And there's a statistic that BA gave out during an Investor Day presentation or similar, although I've now forgotten the exact number given: take a typical trans-Atlantic flight during the summer. During that near year-long selling lifecycle, BA expects to take something like 7 bookings for every physical seat on the aircraft, and then expects to see the aircraft go out about 90% full on the day. Obviously something like 6 of those bookings will cancel (incl date changes) and then there will be a level of no-shows (incl misconnects) on the day. That's another reason why asking how many tickets are sold, or how many tickets are left, would yield a pretty meaningless answer to an outsider.