Flying cars will need to navigate complicated urban landscapes, with buildings, power lines and all sorts of objects to fly around. To move around safely, these vehicles will need to rely on a highly detailed map that shows real-time positions of all potential hazards -- including other flying cars.

Another challenge: Power. It’s enormously difficult to make batteries that are light but also strong enough to support flights longer than a few minutes. A hybrid of gasoline and electricity may be more practical, but that could create more pollution.

But there is hope -- and the answer may lie in consumer drones.

Scaling up these technologies for a flying car -- which is essentially a much bigger drone -- is the key to success.

So let’s take a look at some of the flying car projects that are making progress.

Kitty Hawk

This week, Kitty Hawk -- a startup backed by Google cofounder Larry Page -- released video of a self-flying electric aircraft named Cora. The company says the air taxi can take off and land vertically, so it doesn’t need a runway. It’s also said to be quieter than a helicopter. It's now being tested in New Zealand. 

Ehang

Just two years after it first unveiled a concept aircraft at the CES in Las Vegas, China’s Ehang gave the world a glimpse of its passenger drone in action last month. In a video, local officials and company executives are seen aboard a drone that takes off with the tap of a button and flies over a field by itself.

Lilium

Airbus

Joby Aviation

Volocopter

Uber