Back to this topic, as already mentioned the system will be changed and will be as follows (to replace the current fixed 1-5 size classes for airports):
* Infrastructure size class, levels 1-10. Measurement of available facilities like runways and terminals.
* Traffic size class, levels 1-10. Measurement of airport "busyness", how much traffic (pax) there is yearly.
This is being also modelled currently, the traffic level classes are already being calculated in the background.
However, about the interface. There's an airport size selector for example in the route planning menu and while the existing airport size classes of 1 to 5 will remain in the background (in airport selection in game specific level for example), they will be removed from the interface eventually; so would you just like them to be replaced with the two selectors with 1-10 values or something else?
For other inteface pages, apart from the airport info page, I belive the airport size class info isn't present anywhere?
(Though for now the old 1-5 class system will be still retained, since the infra classes won't change so it's not useful to implement this yet. But I am doing it to the background / technically already since it will be needed in the future)