I know this has likely already been requested maybe even by me, but I wanted to put it out there again.
I would like it if you could add seasonal flights. When adding a route you can check year round or seasonal, and if you check seasonal a pop up will show so you can choose the start and end dates. You would also be able to change a route to seasonal in the routes page or even boost to year round provided you have available aircraft to fly the route.
I also think it would be nice to choose the days if you fly less than one daily. Lets say you fly a route 4 days a week, you would be able to choose the days or at least set it at every other day, or every two days, or weekends only, or just one specific day. Idk how feasible this would be since the months only have 24 days, but I though I'd put it out there.