Nothing illustrates the divide between science fiction and reality better than the flying car. In movies, books and cartoon shows from the mid-20th century, people hop in their car, lift off and fly to work. In reality, we’re still enduring traffic jams or commuting by bus or train. We have supercomputers in our pockets, and deaf people can hear, but the flying car has consistently eluded us. As venture capitalist and PayPal Holdings Inc. founder Peter Thiel famously griped, “We wanted flying cars, instead we got 140 characters” — a reference to the length of a Twitter post.

It’s not that hard to see why the flying car never became the standard mode of transportation. For one thing, the basic technology of vertical takeoff and landing — which is required in order to avoid long runways — is fairly hard. Inventors such as Paul Moller have been working on VTOL cars since the 1960s but made only slow progress — at least until recently.

Flying is also very expensive. It takes a lot more power to lift something into the air than it does to roll something along the ground. Commercial air travel is energy efficient because we pack tons of people into the same airplane, but if everyone had their own flying car, it would cost a lot of money for the fuel.

A third issue is safety. As the world saw on 9/11, the fuel used in a plane — because of its high energy content and volatility — can make a potent weapon. Flying cars also might attain high speeds, making them potentially dangerous should people decide to crash them into things. We’re already seeing how much damage normal cars and trucks can do when wielded by terrorists — flying cars would add an order of magnitude to the danger.

But inventors are slowly whittling away at these issues. Low-cost accelerometers and gyroscopes, as well as better software and processors, have made it far easier to stabilize a hovering vehicle. Advanced lithium-ion batteries have created a safe way to power them, while electric motors have become much more efficient. And incremental progress in lightweight materials has both made it cheaper to fly and limited the damage that a hurtling vehicle can do.

As a result, there has been an explosion of commercial interest in flying cars. A new crop of startups hopes to finally make the 1960s vision a reality. These include Lilium, Kitty Hawk, Terrafugia, China’s Ehang, Slovakia’s AeroMobil and Larry Page’s secretive Zee.Aero. Even large companies like Uber and Airbus are plowing money into the idea. Dubai is working on offering a hover-taxi service using a prototype built by Germany’s Volocopter. Unless these all turn out to be vaporware or white elephants, the dream of the Jetsons future seems inevitable.

There are still a number of serious problems to overcome, of course. One of these is noise. Hoisting a car into the air creates a huge discharge of sonic pressure as rotor blades or jets chop through the air. That’s why even tiny drones are really loud. Imagine much larger and louder flying cars buzzing overhead by the thousand, all the time — that’s sure to put a dent in someone’s property values or quality of life.

The safety problem hasn’t been completely solved, either. Even if a flying car can’t be used as a bomb, it seems fairly easy to use it as a bomber. Having a huge number of high-speed moving objects flying through the air seems like a recipe for crashes of some sort. And air traffic control systems might be hacked.

A third remaining issue is existing infrastructure. Flying cars will have trouble finding places to park. They’d be too big for normal parking spaces, and their inevitable wobble would require some room between parked vehicles.

Of course, people are working on solving these issues as well. Inventors are already claiming to have designed flying cars that are extremely quiet. And other companies are working on software that would — if it could be secured against hacking — prevent a terrorist from using a vehicle for anything other than transportation.

But even the best engineer, corporate executive or political leader will have a lot of trouble getting cities to change their whole layout and infrastructure to accommodate flying cars. The demand for the vehicles would have to be absolutely enormous to get governments to pony up public funds to reshape the modern cityscape. Which brings up the question — do we need flying cars in the first place?

Flying cars could shorten commutes a fair amount. That’s useful, but ultimately a marginal benefit for a very high cost. And since terrestrial self-driving cars are getting closer to being a reality — indeed, self-driving technology probably would be a prerequisite for flying cars themselves — the need to shorten commutes is about to become less urgent. When people are able to do work in their cars, spending 20 more minutes in a car isn’t that inconvenient. That makes it less urgent to spend billions of dollars to rebuild cities to accommodate flying cars, not to mention the cost of the flying cars themselves. And as video conferencing and telecommuting become more seamless, the importance of shortening travel times will be reduced even further.

That doesn’t mean flying cars are useless. The fun of flying, as a leisure activity, is undeniable. In the near future, far more people may have the opportunity to fly without taking expensive lessons and paying for expensive airplanes. But it seems likely that flying cars will mainly exist as expensive sport vehicles, used by hobbyists outside crowded areas. Science fiction dreams are often less grand when they become reality.

Noah Smith is a Bloomberg View columnist. He was an assistant professor of finance at Stony Brook University and blogs at Noahpinion.

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