Wrong.
As demand is huge, you need ridiculous amounts of planes to cover it. As one family alone cannot cover that demand, you must buy atleast two, if not more or even all families possible. Unless an aircraft is economically absoultely unfeasible, it will be bought in larger numbers.
The major problem I see, as has been pointed out, is the lack of passenger transport planes prior to 1930 and data gathering in general.
I agree with this completely. For a world starting this early, demand would have to be slashed to a fraction of what it is currently, otherwise everyone would be buying every last plane they can just to keep up with demand. You'd likely see hundreds of weekly frequencies on routes that aren't even considered trunk routes. I would estimate about 95% or so of overall demand would need to be eliminated to give even some sense of realism here. With the current demand model, this would end up locking out large portions of the world (Africa, Central Asia) from airline service creating a game where everyone is concentrated in the US, Europe, or Eastern Asia.
Yuxi's point about political restrictions is a good one as well. If we had a world going back that early, it would be interesting to have the depression simulated in that demand plummets during the 1930s, but with the huge swings in the global economy and the political instability experienced in the first half of the 20th century, I think there are just too many variables to be able to set up a world that even remotely represents those years with any kind of accuracy. I wouldn't bother with a world that predates the end of WW2.
That being said, I understand that not everyone cares for realism or historical accuracy. Some would rather assemble fleets of old-school aircraft & that's okay too. It is a game after all I guess.