If you take optimizing transportation options as a holistic problem, rather than focusing on any individual user who needs to travel those 50-500 km distances, more trains is a far more straightforward and efficient investment than flying cars, no?
>We also have a much larger airport infrastructure and a complex airspace system that handles the issue of flying over populated areas and flying approaches safely quite well.
Well, yes, at the scale of our current number of commercial aviation flights and a very small number of private planes. You're proposing to kick it up how many orders of magnitude, if we're talking number of air vehicles simultaneously in the air? You need to build an entirely different traffic control system for that, and noise pollution becomes a far more vexing problem. That last one, I'm guessing, is the idea killer if we're talking more than a small number of flying cars. If you ever get to a point where this is an actual concern, i.e. there are actually a lot of them in the air, wait until those rural voters get their hands on you and start contacting their state lawmakers, and until those representatives start law-making.
> So as long as things aren't falling of the plane over someone house (which really isn't a problem even with todays airplanes)
But it is a problem that increases with the number of vehicles in the air.
>I think until we get high speed rail, small airplanes are the next best thing
Is it though? Building good passenger rail (no need for actual HSR) is a solved problem with proven solutions, tested for decades all over the world. How many decades will it take to actually develop a "production-ready" small airplane operable by very quickly trained sorta-pilots, and then deploy the infrastructure needed for N of them to safely operate in an M-kilometer radius? I don't have a good feel for what you think N and M will be, so it's hard to tell. But I'm gonna go ahead and guess it's a far less well-defined question than "how long will it take to connect two cities with 200 kmh rail link".
edit: yes, I'm nay-saying, playing devil's advocate while rooting for the devil just a tiny bit, but I'm not trying to be a jerk, and I am open minded and looking forward to your responses.