I read an article about CAFE with interest, they are in the business of promoting personal fuel-efficient flight.
I think they are right that anyone who has the option of sitting in a queue of cars or up free in the air would choose the latter, but the point I think they miss is that the ground is so congested because there are so many people wanting to get somewhere, who all have the money to have their own vehicle. Over a hundred years or so ago a few people had cars and frankly the only thing to get in the way was pedestrians and horses. So no congestion because noone else could afford to have a car.
Roll forward a hundred and thirty years and all those early adopters will spend goodness knows how much to get flight, just as all us folks from council houses start aspiring to it. Roll forward 50 years and us plebs will all have planes too and we’ll all be flying in circles in a stack over the Pentlands while traffic control shows us a red light to stop at a junction.