Since Curtiss Aeroplane and Motor Co. first showed its Autoplane prototype in 1917, most of the development work on flying cars has been focused on vehicles that might more accurately be called "roadable airplanes" — that is, they can be flown and then later driven on a road. With few exceptions, most of these have been winged two- or four-passenger vehicles.
Like the Curtiss Autoplane prototype, many of these roadable airplanes — the Terrafugia Transition and AeroMobil are modern examples — have employed mechanisms that allow the wings to retract or fold when the vehicle is on the ground, making it narrow enough to navigate in traffic with other cars. But there have always been baked-in problems with this type of design, including excessive noise, safety concerns, the need for runways and the need for a pilot's license. There is also the requirement to meet rigid aviation safety regulations as well as nettlesome and costly automotive safety regulations.
Those compounded requirements have proved burdensome, to say the least, for some inventors. Take 80-year-old Canadian engineer Paul Moller. He's been chasing the dream of a flying car for over 50 years and developed the M400 Skycar, a vertical takeoff and landing vehicle, that made its first test flight in 2003. Moller explained that stringent automotive safety regulations were the reason his Skycar design had three wheels instead of four, classifying it as a motorcycle under federal law.
"If you've got to deal with the crash-protection issues of the automobile, forget it; you're never going to fly it," Moller explained in a 2004 TED Talk. "If you're going to fly like that, you're not going to spend much time on the highway."
If history proves anything, it is that cars and planes probably don't mix — except in the minds of inventors.
"The smashing together of a car and an airplane makes neither a good car nor a good airplane," Embry-Riddle's Anderson said.
Yet the burning desire to build a flying car keeps even some famous inventors thinking about overcoming such obstacles.
"We could definitely make a flying car — but that's not the hard part," Tesla CEO Elon Musk told a London audience in 2014. "The hard part is: How do you make a flying car that's super safe and quiet? Because if it's a howler, you're going to make people very unhappy."
While roadable airplanes remain a long shot at best, experts agree that at least some automotive functionality soon will move to the sky.
Among the most likely to arrive first: point-to-point autonomous airborne ride services that one might employ to travel, say, in New York between LaGuardia Airport in Queens and a landing pad in midtown Manhattan, bypassing gridlocked traffic. Such vehicles likely wouldn't have wheels or spend any time on the streets. Instead, they would fly distances of about 25 miles or less (making important variables such as weather more predictable), be electrically powered with multiple rotors and fly completely autonomously.
In other words, a large drone with human cargo, or an Uber Black for the sky.
"The way helicopters pick up rich people and take them from place to place out of traffic? That's what you're going to see, except with drones," said Don Hillebrand, director of the Center for Transportation Research at Argonne National Laboratory in suburban Chicago. "It may not be five years from now, but it will happen."
Some well-known companies in the aerospace and automotive industries already are preparing.
At this year's Geneva auto show, aerospace giant Airbus teamed up with Italdesign, an automotive design and engineering firm, to display a concept called the Pop.Up. It comprises an enclosed, two-seat, carbon-fiber pod that autonomously attaches to either an eight-rotor flying module or a four-wheeled ground module, depending on where the passengers need to go. Both modules would be battery-powered, the two companies said, and each module would return to its charging station when not in use to juice up and await its next call for service.
"I think, right now, the urban sky is quite underutilized, and that's exactly the proposition," said Mathias Thomsen, general manager for urban air mobility at Airbus. "The gridlike layouts of roads doesn't actually do it for us. We think that by combining air and ground, we will get a much better use of the space than we have in our cities."
Thomsen said Airbus' appearance in Geneva, its first at an auto show,, was "a reach-out to the whole automotive sector, which we see coming closer to us in the development of urban air-mobility vehicles."
He said the vehicles that do make it to market "are going to be small, just like the automotive sector is used to, but underneath, they're going to have to be safe and reliable to fly, which is what we're used to."
Terrafugia, which was founded in 2006 by a group of Massachusetts Institute of Technology graduates and will remain in suburban Boston under Geely's ownership, says it's close to finally launching its first product. It's aiming for a 2019 introduction of the Transition, a folding-wing two-seater that it displayed at the 2012 New York auto show, followed by a vehicle capable of vertical takeoff and landing in 2025.
Uber, meanwhile, after broaching the idea a year ago, now says it aims to demonstrate aerial taxis in several cities by 2020 and launch a full network in 2023. By the time Los Angeles hosts the Olympic Games in 2028, customers will be "making heavy use of air travel," said the company's chief product officer, Jeff Holden.