The idea of flying cars is seriously old.
Probably the first attempt worth noting was the Curtiss Autoplane prototype in 1917. It was an aluminium closed car, styled of the era, with tri-plane wings from a Curtiss Model L trainer attached, and a four-blade propeller at the back. However, it only got to do a few testing hops before the project was terminated as the USA entered WWI.
Many other designs have reached the stage of fully-functional prototype, but two from the 1940s actually received approval by the USA's aviation authority.
The Fulton FA-2 Airphibian in 1946 was actually a small airplane made capable of using the road, not a car made to fly. Also, the wings, fuselage and basically everything behind the two-person cockpit was detached for road use, as was the nose-mounted propeller. Only four prototypes were built before a lack of funding ended the project.
The (Taylor) Aerocar was first seen in 1949. There were only six built over the next 17 years or so in varying specification, but each one was a small car with wings attached, and these too dispensed with the flying gear to use the road. These also put the propeller at the rear like the Curtiss, indicating that the 1917 creation could probably have been made to work, given the opportunity.
So, if they've been around for over a century why aren't we using them already?
Well, it's because they're actually a genuinely terrible idea that solves nothing
Whatever the design, it's a very expensive tiny slow aircraft with limited range and the poor practicality of a tiny slow car.
The other problem with those 1940s designs is you also still needed a landing strip and a hangar, and a pilot's licence.
Some other designs (including current ones) are more like small helicopters with a single rotor for lift, or several small rotors like you see on camera drones.
Modern designs can fold the flying gear (of whatever type) away for road use, but even so you still end up with something that's slow in the air and not very practical on the road.
These things are touted (or assumed) by some to alleviate traffic congestion, but that would mean having quite a few of them in the air to replace enough cars on the road for said congestion to be eased, which would then cause them to have their own congestion problems because they need much more personal space to operate.
That benefit is redundant anyway. First up, the powerful or rich (who could afford to run a flying car) already achieve short custom flights with helicopters. That's what Kobe Bryant was doing on the morning of January 26, 2020 with daughter Gianna and seven others on board when the pilot got disoriented in the fog and crashed into a Californian hillside. All nine people perished.
That raises another point. If you think flying cars won't also fall out of the sky or run into things in bad conditions, you're kidding yourself. They'll need to be grounded instead, so roads on wet and foggy days will still be clogged. Oh, and if you think that your scheduled servicing and annual roadworthy checks are an inconvenience now, the essential routine of pre-flight checks is not for you.
Beyond that, even when they do successfully complete a flight, they need somewhere to land that's closer to your destination than the congested roads you wish to avoid. Otherwise those sections of road will remain just as congested as they are now.
Furthermore, any small aircraft I've ever been in has been terribly uncomfortable and noisy, which is another major issue. Moving enough air to fly makes a lot of noise, even if the motors are electric. And there's no way the general population will accept the noise of one landing near their homes, further limiting the ability to bypass any areas of congestion they're trying to avoid in the first place.
Also, don't ignore the point that they will use stupid amounts of energy compared to driving. One argument for them is electric propulsion, but batteries are heavy, and the world demand for electricity is already increasing way faster than renewable sources of power are coming online, which means even electric ones will increase greenhouse emissions. So while it sounds like flying cars is a feat of human advancement, for now they'd just hasten our species' downfall.
