As for taxi-ing, ever noticed how few tiles a flying aircraft travels in a single day, even at an incredible speed of 500-something km/h or more?
Tiles must be enormously big.
In general, scale in OpenTTD doesn't exist, or rather, everything has its own scale, namely one that works for the game. As such, trying to relate one scale to another is a useless exercise, it makes no sense.
Nonetheless, I agree with the idea of having modular airports, it would expand the scope for building an interesting air transport system a lot.
I agree the scale is not very relevant as long, as things go smoothly. But I think the current loading parameter is too much out of scale.
Seems there is bit of misunderstanding.
My perspective on this is someone, who tries to design new airport (I tried that long ago in OpenTTD). Now, when you want to design new airport and whatever tools you have - current state machine or something new in the future.
You will run into weird limit. And the limit is effective Gate/Runways ratio. Current airplane movement and loading counts with very few gates to runways, something around 2 gates per runway. You need A LOT of runways. And this create strange looking airports and you run into design limit around 8 runways.
To make possible of better looking and less limiting airports I suggested to make planes spend more time at gate, such as they do in reality. The parameter for this is loading speed. In my opinion planes should load 5 or 10 times slower.
Loading speed of aircraft is solely decided by the aircraft, airport has nothing to do with it.
Once you noticeably change loading speed, you need to redesign current airports, because there will be bottleneck on those too few gates, it's all connected.