top jock
When you take off you are nailed with Euro Control Fees. I have been told that Ryanair pay more on Euro Control Fees then they do on fuel. Trust me it is not free.
Sure, I can understand that but, I guess, one advantage is that the costs are predictable. For the railways, when a truck bumps into one of their bridges - all traffic is stopped until an inspection is made. If a repair has to be done, then you have to pay human beings at overtime rates and pay for busses etc. Lastly, if there is a break down or incident, it can close the railroad to all traffic for an hour or a week. If you meet 'bad' air, then you can reroute until it has blown over.
I am not suggesting that this is a full comparison but is one of the reasons that rail can be more expensive. Of course, since the railways adopted the airline's yield management, they have been able to make more money.