Sketched by Da Vinci in the 1480s, working prototypes now exist of machines that fly with an orchestration of gliding and flapping their articulated avian-like wings.
An articulated wing combines the vertical lift and maneuverability of a helicopter with the range, energy efficiency and safety of a large winged glider.
Cheap motorized toy flying birds are not fully articulated. There isn't a computer onboard to drive all the different dynamic configurations of the wing shape nor do they have the complex wing design, in order to increase and decrease lift and transfer lift to thrust via the angle of the articulated 2D degrees-of-freedom joint between the inner and outer half of each wing.
Toy birds have a constant lift versus horizontal thrust ratio because the pattern of the flapping motion can't be varied, thus the only variable is the speed of the motor. They fly higher and horizontally faster, or lower and horizontally slower. They can't fly higher while moving slower horizontally or vice versa. They can't vary the horizontal speed independently of the vertical speed, as a real bird can.
Due to the lift from their large wings, gliders don't crash to the ground when the engine fails, thus are potentially much safer than the 85 times higher fatality rate of helicopters versus cars. Articulated wing aeronautics doesn't require a runway for launches and gentle landings.
The safety of helicopters could in theory be improved with computerization to simplify the complex navigational controls and automate safeguards on navigation, e.g. an onboard computer could prevent a helicopter from flying too close to terrain or upside-down. Articulated wing aeronautics require computerization. Computerized driverless cars are projected to be ready for sale by 2020.
Yet the safety of helicopters is unlikely to approach that of articulated, gliding wing aeronautics because:
The large wing needs to be articulated for the flying aircraft to have the launching, landing, and maneuverability required for a flying car. Also an articulated wing might be designed to be tucked away when not airborne similar to a bird when perched.
Autogyros a.k.a. gyrocopters (or gyroplanes) have flight characteristics that are a mix of an airplane and a helicopter gaining the safety advantages of both such as navigational control in event of engine failure and no stalling at slow speeds. Autogyros are simpler to maintain, because the blade is not powered (except optionally only at and for more vertical takeoff and landing). This mechanical simplicity has enabled the production of the first viable flying car prototype which complies with international laws.
Large wing aircraft are as energy efficient as cars.
Whereas, helicopters consume roughly 7 - 15 times more energy than vehicles to transport the same payload and distance. For example, the lightweight Reynolds R22 two-seater consumes 9 US gal (30 l) to transport a 440 lb (220 kg) payload 110 mi (176 km) in an hour. That is 12 mpg (6 km/l) compared to 80 mpg (40 km/l) for a 2 passenger 125cc motorcycle. Ditto 12 mpg $20,000 ultralights but only for a single passenger. Five passenger helicopters consume 36 US gal (120 l), thus 3 mpg (1.5 km/l) compared to 40 - 55 mpg (20 - 28 km/l) for a small, fuel efficient 5 passenger car such as the Volkswagen TDI.
Autogyros are no more efficient than helicopters.
Flexibility and personal freedom are other measures of efficiency that are very important to the economy; which is why we prefer and are more productive with cars even though trains are 10 times more energy efficient. Yet all of humanity probably can't afford to consume 10 times more petrol for helicopter transportation.
Any lightweight glider (i.e. the articulated wing) is vulnerable in high winds. The articulated wing can't hover motionless nor move slowly in tight spaces as a helicopter can. Unless some sort of magnetic acceleration (perhaps employing a supercapacitor charged from the engine) can provide the initial jump, the articulated wing can't launch vertically from a standstill.
The Harrier Jump Jet possesses greater maneuverability, top-speed, and high wind tolerance than the helicopter, yet consumes 10 US gal (37 l) per min. With higher energy-density, flying cars could have these more flexible propulsion systems and carry more payload thus storing backup propulsion energy in batteries for increased safety. Nuclear energy has orders-of-magnitude greater energy-density than petrol. If nuclear-power is ever commercialized for personal transport, it might achieve the efficiency to supply the required vertical thrust so the large, gliding (articulated) wing is not needed.
Thermal engines based on any heat reaction such as petrol, chemical reactions, or fusion, are limited by the engine cycle efficiency and the relative engine-to-ambient atmosphere temperature in the equation for Carnot efficiency. Thus are limited to usually about 40% efficiency. Matter (except for dark matter) exists in four possible states; solid, liquid, gaseous, and plasma. The first three are comprised of atoms with electrons rotating around a nucleus, and plasma contains free electrons a.k.a. ions. Plasma engines thrust with ions and thus are efficiency limited by the relative quantity of ion reacting mass in the atmosphere. However, as a cutting torch demonstrates, plasma can be used to superheat the fluid before it reaches the atmosphere.
The invention of the automobile diminished the railroads and the railroad stocks crashed in 1907, thus reducing the relative value of the land nearer to versus farther from the railroad tracks. This diminished monopolies (e.g. Rockefeller's Standard Oil) and Olson political capture of the sparse resource of railroad tracks, thus expanding freedom and economic prosperity. The flying car should do the same w.r.t. to roads.