<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by IncyWincy:
... that F4 A4 really means there are 4 seats and therefore one First Class passenger in either subclass taking up a ticket will diminish both categories by 1 - this I understand. Yet on the other hand you effectively said that F4 A4 meant the airline intended to sell 8, I thought, on your logic, it would mean they intend to sell 4?</font>
Figures like Y9 are
NOT seats - but tickets. Airlines typically oversell flights, too. Y9 just means that you can buy at least 9 tickets:
a) it may be possible that you are the first customer for the flight and there are still e.g. >200 tickets available.
b) it may be possible that the plane is actually overbooked and therefore there's theoretically no SEAT any more available if all customers show up. The airline still sells tickets and expects last minute cancellations and no-shows so that at the time of departure number of tickets = number of seats (in an "optimal" case).