The dream of personalised flight is still vivid in the minds of many inventors, some developing cycle-powered craft, others pouring money into jetpacks.

However, the flying car has always remained the ultimate symbol of personal transport freedom.

Several companies around the world have produced prototypes that can drive on roads and fly.

Airbus has a futuristic modular concept involving a passenger capsule that can be detached from the road-going chassis and picked up by a helicopter-type machine.

But all these concepts are massively expensive, require safety certification standards for road and air, need dual controls, involve complex folding wings and propellers, and have to be flown from air-strips.

So they are likely to remain rich people's playthings rather than practical transport solutions for the masses.

"A car that takes off from some London street and lands in another random street is unlikely to happen," says Prof. Gray, a leading aeronautical engineer. "Sky taxis are much more likely."

But that won't stop inventors from dreaming up new ways to fly and trying to persuade investors to back their sometimes outrageous schemes.

Civilian aviation is being disrupted, not by the age-old desires for speed, romanticism and glamour, but by the pressing need to respond to a changing climate.

New electric engines coupled with artificial intelligence and autonomous systems will contribute to a more efficient, integrated transport system that is less polluting and less noisy.