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.
So basically LHR would eventually be 10/10, while some ex-military airport with long runways serving only some cargo or charter flights would have high infra level but low traffic level 8/2 for example.
* All airports start at infra level 1-5, corresponding to what has been assigned today as a size class value (or alternatively this can be counted from number/length of runways etc but it's not that good as it does not take into account terminal capacity which the pax count does see). Infra class level cannot go lower but it can go higher (see below).
* Traffic level is determined on which percentile of world airports this airport goes (from airports that have >0 pax/cargo transported). The highest 10% of pax transported per year will be at traffic class 10, next 10% at class 9 and so on. For the first game year this is calculated from the preset database values (real life stats) and from year 1 onwards the values are calculated according to actual passengers transported to each airport by players' airlines.
* Traffic class can change by 1 step per year on both values either direction. 1 minimum, 10 maximum.
* Cost of airport operations (landing fee, handling fee, pax fee) will be determined by a combination of these two figures (infra+traffic = cost factor), similar to today's 1-5 levels.
How infra level can get higher?
* For this I'd plan a new feature called "airport expansions". This is a reply to the slot situation at some airports and also especially to make the airports even more dynamic.
* If the airport is getting crowded ( 1) running out of slots, or 2) getting much more passengers than what the capacity (traffic class) is) then the airport will start to plan an expansion. Depending on game year (and possibly world area?) the expansion plans will take X years to complete (let's say 5 years). When the expansion is completed new slots will be allocated (new runway) and the infra level will go up one step.
* There would be a limit on when the airport can expand again after previous expansion (let's say 5-10 years after previous has been completed they can think of new expansion, so the time between two expansions would be 10-15 yrs). But theoretically a tiny regional airport could expand from level 1 to all the way to level 10, meaning that it's capacity would grow from somewhere at 5 slots / hr to 100 slots / hr (just to throw in some random numbers). But this of course takes tens of years.
* This expansion process cannot be funded by players, as runways and such are not funded by airlines. Instead the airport collects the money from you as the airport fees... Higher infra level = higher fees.
* Also idea is here that each game starts in the 1950s so there is plenty of time for expansions. If we're doing short games that start in year 2000 for example having infra class 5 wouldn't be a problem as it's only a cost calculation value, the amount of basic slots would be calculated as per current system still - or alternatively the starting infra size classes can be a factor of the initial game year, so start up in 2010 LHR is already 10/10 airport. But for games starting early and going on for a long time the initial airport capacity for some airports (for example ATL already at 40 slots in JA) would be smaller.
And to add, these figures would not really affect the pax calculation so far at the first point of implementation and with present demand systems, just to the ops costs etc and the possiblity to get more capacity, and especially a feature to enable all sorts of dynamism in the future .
..also something I forgot probably. But please discuss.
(note so self, see also duplicate thread: http://www.airwaysim.com/forum/index.php/topic,16679.0.html