#6.  These Flying Machines Of The Future Would Have High Fuel Costs

Operating compact cars that could double as road-legal, four-wheeled vehicles on backgrounds, interstates, highways, city streets, and everywhere else modern cars and trucks travel would be incredibly expensive. It would likely require two types of fuel – one for driving, one for flying – and the high number of takeoffs well-suited, efficient flying patterns would require would make these hypothetical automobiles far too expensive to be used practically.