Cargo

[Zortan]

Events when implemented would both increase and reduce demand depending on the type of event.

That is true. But why not just increase passenger flow in those seasons where they really do increase in the real world? No need to specifcally do them for holidays.

Seasonal demand is interesting but I think that's a separate thing, i.e. certain areas having increased demand in the summer or the winter. But I'm not sure how exactly to implement it without manually applying a modifier to each airport

True, that would make it difficult for the seasonal demand. But there are some general assumptions you can make. For example demand between North America and Europe is really high in the summer, while demand between north america and sunny places (especially the caribbean and hawaii) is really high in the winter. Demand for tourism in europe, short or long-haul, is higher in the summer than the winter, with the exception of skiing (so INN, SZG, some places in switzerland etc). There is more seasonal demand I believe but that's most of it.