A bit of a tangent, but interested people might want to look at https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft
The most efficient aircraft per passenger is a Bombardier CS300 over a range of 1900km... 1.85L/100km. That compares well to most ICE cars if they're carrying less than 3 or 4 people. Of course, 4 people in a car is about as cramped as as airline seats. A full 63-seat bus averages 0.41L/100km per seat.