There are many claims regarding flying cars today. They are all just small modified airplanes. They can never function as cars for small distance intra-city personal transport.
While planes travel from airport to airport and are assisted by air traffic controllers while landing and take-off, flying cars shall need to take off and land from /to just about anywhere. You cannot have air traffic controllers everywhere, in front of every house, shopping complex, office, etc. Risks of crashes shall multiply millionfold.
Planes are flown by trained pilots and given flying license after several hours of flying experience. It will be very costly and time consuming to train practically entire populations to fly these cars
Cars are supposed to have brakes, and must be able to take quick and even short radius turns. Planes have no brakes and change direction over a large radius only. For braking, there is no friction in air as on land between car tyres and road. Friction and low speeds allow short radius turns that are impossible in an airplane. We have very few planes flying in the air at any given location and altitude. With cars that are for personal transport, we would have millions of cars in any large city and there could be several cars flying in the same location and altitude.
Planes are checked and certified by aircraft maintenance staff before every flight to ensure that they are fit to fly. This is necessary because if a plane develops a snag mid-air you cannot stop mid-air and get down to check the engine. The plane will fall from the skies killing all on board and others on land down below.
It is seemingly impossible to check every flying car in every citizen’s garage before every flight. There would be millions of cars taking off any minute in a big city
Airplanes have sufficient fuel so that they do not run out of fuel and drop off air. This is ensured by airlines staff that is strictly monitored by aviation authorities of various countries. Who is going to monitor fuel tanks of millions of flying cars when they become available to all common citizens
Planes travel on predefined routes to avoid mid-air collisions. How do you define routes for millions of cars and ensure that everyone follows them.
When there are no defined routes, flying cars would crash against each other. Why? Because while driving on road you only need to look ahead and occasionally in rear view mirror. In case of flying cars other flying vehicles could come flying from just about any direction. It is impossible for a human driver to look out in all possible directions (ahead, behind, left right, above and below) and also control the flying car, take corrective action in time without the facility of brakes and steering that takes quick sharp turns.
No one would be safe anywhere when cars begin to fly. You could be walking in a garden or sleeping in your home but could be a victim of a falling car that has lost control or developed a snag.
Security of all VIPs would be compromised. Presently, it is possible to barricade roads and deploy security persons on the roads leading up to the high security areas. But with flying cars, it is impossible to put barricades in air. We could have several 9/11 type attacks.
Flying Cars could also be used to drop heavy objects, even explosives on chosen targets.
Mid air crashes would often result in large number of casualties. Two cars that crash in the air would fall down and could possibly hit many other cars flying below them as they cross their path while falling. Several cars would fall to ground causing huge damage and multiple deaths including deaths of people on the land below.