I have 2 S slots and multiple arrivals to IAD as per the default. However, the slots are not used often due to no arrivals despite everything else being available.
You have to buy more flights in the routes tab. This was implemented in the last update.
I already have 5 S routes for 2 S slots though
You have 5 routes for 2 slots which are on picture full. You need to empty one to get new arrival.
The slots I’m talking about are S slots, and those planes are well on their way to the runway. So I don’t think that’s the issue.