Proving that reality is trying to catch up with fiction, a few manufacturers are working on modern Jetson-style flying taxis. But they won’t cut it, says MIT researcher Carlo Ratti in an op-ed in France’s Le Monde.\nCity skies swarming with flying vehicles have been a staple in science-fiction movies, from Fritz Lang’s Metropolis to The Jetsons, Blade Runner and Star Wars – Attack of the Clones. Today, Uber is investing in a flying car, Airbus has designed an air taxi called Pop.Up, and a German startup called Volocopter recently tested an 18-rotor miniature helicopter in Dubai.\nMeanwhile, with sales projected to hit seven million units a year in 2020, drones are already hovering everywhere and many anticipate they will soon be carrying not only parcels but people, dropping them off at restaurants and movie theatres.\nBut such dreams will come up against very practical obstacles. For one, using rotors to lift a heavy weight causes considerable turbulence and noise – a problem that New York City knows all too well, since it has limited tourist helicopter flights to 5,000 a month. Imagine eight million citizens taking to the skies.\nEven with improved battery technology and increased autonomy, drones and mini-helicopters transporting people would present considerable security risks. A crash would not only endanger passengers, but also many others in densely populated areas. And it’s not certain that these fully computer-operated vehicles could resist hacker infection or terrorist takeover. How would cities control dense air traffic? It’s hard to put traffic lights 1,000 feet above Fifth Avenue – even if the various flying vehicles could obey them.