Air travel less harmful to the environment than rail travel?

Air travel is probably less harmful to the environment than rail
travel. Aircraft leave vapour trails which aid in the reflection of
the sun's radiation back into space. As these trails are at high
altitude their shadows cover immense areas. On the other hand vast
quantities of fossil fuels are burnt to produce the electricity (at
only 10% efficiency) to power the railways. If someone would do the
calculations, all things considered (the upkeep of track and bridges
for instance) they would probably find that Aircraft are less of a
cause of global warming than an equivalent railway system.