Like many buildings in California, Uber’s San Francisco headquarters features a defunct rooftop helipad. Many were mandated by the state as a way to evacuate people during emergencies in the seismically challenged region. But even if building owners wanted to offer private helicopter service, economics and public outcry would probably stop them. While science fiction gave us hovercars floating serenely across the sky, reality gave us obnoxiously loud helicopters beating the air into submission–something few commuters can afford and nobody wants to hear. But a convergence of maturing technologies has Uber and dozens of other companies betting fortunes on the decades-old dream of quiet, inexpensive, even eco-friendly air taxi service. How affordable might these phantom air taxis be? Uber claims initial prices will be comparable to those of its luxury private car service, Uber Black. As I write this story, Uber’s app is quoting me a luxury car service fare of $84.14 from the center of San Francisco to SFO airport. Eventually, claims Uber, per-person prices for its air travel service will be similar to its taxi-like car service, uberX ($37.48, at the moment, for that same ride to the airport). What makes such low fares even remotely plausible? With batteries charged on cheap electricity, clusters of small propellers that are quieter than the thunder of big helicopter rotors, and the ability to transform from vertical lift to airplane configuration, these imagined aircraft-of-the-future promise to substantially cut noise, cost, and the risk of accidents (like the fatal March helicopter crash in New York City). The projected time frame for delivering these largely speculative craft, and for building physical and technological networks to support them? A mere five years. They would start out as human-piloted vehicles–but per Uber’s sales pitch, would evolve into fully autonomous ride-sharing flyers.