Should we have seasonal demand? (i.e. Miami gets more flights during spring and summer, and popular ski areas get more flights during winter)
This is actually pretty easy to implement actually because barring the major transport hubs (those that aren’t affected by seasons), your latitude is proportional to the number of visitors you get.
So generally it looks like a curve (demand) and the apex of the curve is the particular time of year calculated by latitude. The further away one is from the Equator, the further away business is from summer; i.e. the distance to the equator is directly proportional to the amount of time away from summer in which there is peak activity.