When humanity has been replaced with robots. At least as drivers. Yes we have the technology for flying cars, or small personal flying transportation. The reluctance to unleash that technology on the world has much to do with the 40,000 traffic accidents per year (USA alone) that are fatal and the million or so other traffic accidents. (USA only - much more when we consider global statistics) There is respect for the logistics here. Its bad enough that cars sometimes fly off the road into houses - imagine if cars crashed and fell from the sky too. Great strides have been made in modern avionics which means that some of those jets can take off, fly to their destination and land all on their own. We are taking millions of dollars worth of electronics which are presently way to expensive to slip into personal family fliers. Robotics and computer A.I. technology has taken leaps and bounds and appears to have a longish future of such growth. It may be less than 20 years down the road when a cheap, reliable auto-pilot will be built that can be mass produced to not only take off, fly and land a personal aircraft but will also be able to change flight plans and make the private flier a reality for the average family. Another wall we are reaching is energy from fuel. Oil prices keep going up, and too there is the issue of pollution. Land vehicles are more efficient for short trips, say across town or across a state/region. Flight uses up too much fuel for flight to make flying to your corner market a worthwhile trip. No one has invented a real gravity repellar or a usable ion field generator that can be applied to a flying craft. We still chiefly rely upon propellers and jet turbines to produce power for any flying craft. These come with their own safety issues which have to be considered.

When they stop handing out licences at the McDonalds drive-thru....people can barely drive while they are on the ground....could you imagine if they were in the air??...;)