The flying part is relatively easy.  The hard part is that the cars will have to be programmed to a destination and be self flying on a specific course via AI.  Also, all aircars in the area will need to be linked to a wireless high speed AI network so that each car knows where all the other cars are flying to avoid accidents.  They do have an opportunity in this area; unlike regular ground cars that have none of this tech and would take decades to have all cars have it and be compatible.