[loufe]

The thing is, the cost of building rails is amortized over, in some cases, well over a hundred years. Most of train travels emissions are fixed emissions, marginal emissions being much lower. On the flipside, air travel has a much smaller fixed emissions amount but drastically higher marginal emissions.

Also, it is not my particular field of engineering but there is likely no scenario where fuel efficiency of planes is better than trains. That you can find sources for pretty easily.