Reply #9: Fuel is definitely an issue as well.

[Ready4Change]

Fuel-wise, Jetsons/Star Trek assume plentiful and nearly free energy.

Large airliners can get surprisingly good fuel milage per passenger. As much as 60 mpg when fully loaded, figured for a Boeing 777. However, the smaller an aircraft gets, the worse it's fuel milage per passenger becomes. In the end, as long as you don't need to get where you are going very quickly, ground transportation will always be more fuel efficient.

So, a single passenger air car, especially in helicopter form, trying to get some where quickly, is about the worst milage vehicle you can envision.