I'm not sure I understand your example very well or what you are trying to say.
> Consider an empty plane where all the seats are paid for by passengers that all coincidentally were late to the airport. That's not a problem for the airline, because the tickets got sold and it was the passengers fault. However, this is a failure for the tube, for which payment is secondary
In both cases, the airline and the tube have fixed costs related to having planes flying or trains running. For both of them payments are necessary to offset the fixed costs and generate profits to further invest in better transports.
They key difference is that for one the volume of passengers is much higher than the other, therefore "full capacity" is defined in very different terms in the Tube vs a plane. People don't stand in a plane like they do in the Tube.
> Consider an empty plane where all the seats are paid for by passengers that all coincidentally were late to the airport. That's not a problem for the airline, because the tickets got sold and it was the passengers fault. However, this is a failure for the tube, for which payment is secondary
In both cases, the airline and the tube have fixed costs related to having planes flying or trains running. For both of them payments are necessary to offset the fixed costs and generate profits to further invest in better transports.
They key difference is that for one the volume of passengers is much higher than the other, therefore "full capacity" is defined in very different terms in the Tube vs a plane. People don't stand in a plane like they do in the Tube.