In the US, we would probably drive our own cars anywhere within a 250 km (150 mi) radius, which costs about $170 in fuel and vehicle maintenance, and takes about 2 hours each way.
Tax flying in the EU, and people will likely take more trains. Try it in the US, and you're just pushing people back into their cars.
Airliner aircraft burn more fuel closer to the ground, at takeoff and landing, and less fuel at cruising altitude, where the air resistance is less. On shorter trips, the proportion of the trip spent at lower altitudes is greater. Some flights might not reach optimal cruising altitude at all.
One can adjust the flight profile for maximum fuel efficiency, but this tends to be uncomfortable for the passengers and crew, and it takes longer to reach the destination. Most US passenger airlines don't do that, but military and cargo carriers will.
That aside, some portion of the fuel is spent continuously keeping the weight of the aircraft aloft, and with ground vehicles, the equivalent expenditure is the rolling resistance of the tires. Furthermore, an airliner plane tends to carry all the fuel it needs for the entire flight on takeoff, which translates to additional weight, whereas the ground vehicle can refuel enroute at a truck stop or gas station. Some aircraft can refuel in flight, but another plane has to carry it up there and maneuver it into place. A train on electrified rails need not carry any fuel at all.
So to some extent, it depends on the ground vehicle and the aircraft. In a contest between an ultralight or powered paraglider and a heavy pickup truck towing an RV trailer up in the Rocky Mountains, the flyer might have a lower footprint. But for a trip over flat ground, such as Chicago to Indianapolis or Cincinnati to Cleveland, in a medium-sized hybrid ICE+battery sedan, driving at or below the posted speed limits on US Interstate or Autobahn-like restricted access divided highways, I think the car will win against anything other than a solar-powered lighter-than-air craft.
I haven't done the bar napkin math, so I could be wrong.
Tax flying in the EU, and people will likely take more trains. Try it in the US, and you're just pushing people back into their cars.