This is in response to the request made on the steam thread that I started. Upon loading this save, I get hit by initial lag, which is resolved quickly by zooming in. This is clearly a fault on my side with regards to my graphics card not being fast enough. After running smoothly for a several minutes, (anywhere from 15 mins to an hour) the game starts to drop in fps, until eventually it becomes too laggy to play, even when zoomed in and if I haven't made any changes to the airport and just let it run by itself. This means that the game seems to be experiencing memory leaks, especially as this issue can be resolved simply by saving and reloading.
On smaller airports, I never experience this, but on larger airports the game runs smoothly for only a few minutes before it has to be saved and re-loaded, presumably because there is more going on and therefore more memory is being used and then not freed up once the process is finished.
TLDR: ACEO needs better garbage collection as memory leaks can require players to re-load very large airports every couple of minutes, which is obviously frustrating and time consuming.