Flying cars still seem like one of those futuristic technologies that only exists for now in the realm of science fiction and old episodes of The Jetsons. But Uber is taking the technology seriously and this week it takes another step forward with a summit meeting that lays out its vision. In October, the ride-hailing giant published a 97-page white paper laying out all the challenges for setting up an urban flying taxi system to link with its on-demand car service.