@davidho There's another difference.

Trains require a vast land take and tens of thousands of miles of track (in the EU, to pick as an example) and signalling to maintain. OK, so ATC infrastructure isn't trivial, but it needs considerably less land take and hardware on the ground to get a plane from one end of the journey to the other than it does a train. (And, OK, yes, when you do get to the end an airport is typically rather larger than a railway station.)

Now ... these differences are obvious, but what I don't know is how that translates into numbers and affects fares.