There already are real flying cars though. They are vehicles with wings that extend out from the car's body and can take short flights. They fly in the sense of what people expect from any other plane -- and thus need flat ground to act as a run way. None of these designs use cold air thrusters because its simply not viable for extended flight.

The reason thrusters work well in space is minimal weight there. You need to work many times harder on Earth to counter act the weight of the object here.