This seemed ... odd. Surely being crammed in like a cow in an abattoir truck gets airplanes something. So I looked it up https://en.wikipedia.org/wiki/Energy_efficiency_in_transport

For the curious: Boeing 747-400: 3.1 litres / passenger 100km, or 91 passenger miles per US gallon.

Better than ICE car with 1 person in it, and modern planes do better. It turns out the lower temperatures at 10km above sea level helps both the Carnot efficiency and drag. But the 747-400 travels just under the speed of sound, which hurts. Slower airplanes (but still faster than any land based transport), get you a 2 or 3 fold improvement.