There are always tradeoffs... airplanes move more or less at a steady speed, and are much more aerodynamic than cars, which spent quite a bit of time stuck in traffic. Thus in many cases planes are more efficient than cars (despite needing to lift).
Airplanes have to go faster than the stall speed. Stall speed is typically ~60mph or more, and air resistance goes up as the square of the speed (times the aerodynamc cross section). Airplanes aren't really that much more aerodynamic than modern cars.