One piece of information about the airline industry is that there are specific dates when airlines submit schedules to airports and this can be different from when they make flights available to purchase. This is why it can be troublesome if you book a ticket too far in advance because the schedule on the airline's website is what they expect their schedule to be, but airlines are always evaluating routes and cities based on supply and demand of passengers and even when passengers want to fly, so sometimes they change the schedule. Airlines will even trade their slots with other airlines if it's past the schedule submission deadline. Airlines are given certain slots based on their historical flight operations, but sometimes the airline decides to change flight time or even drop the airport all together or add destinations all of which affect flight schedules across their network. Here is a link with more information, it's pretty long, but worth a skim or "command/control F" to learn at least a little bit. http://www.wwacg.org/up/files/DocsWSG/WORLWIDE_SCHEDULING_GUIDELINES/WSG2-Jul00.pdf
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