the problem with comparing these things by their ticket prices is that markets don’t consider externalities. making and fueling a plane might allow me to sell tickets cheaper than a train, but only if we ignore the cost of the carbon output (since neither the flyer nor the airline pay for this, but society at large does)
i wonder how this comparison would shake out if you included a carbon tax that effectively measured the cost of these trips on the globe.
A SF -> NY round trip direct flight costs $362 and emits 554kg co2e according to google flights. The price of carbon by various emissions trading systems vary from less than $10 to almost $100 per tonne[1]. Of course, you could argue that such systems aren't fully capturing the cost of carbon, and therefore using prices for those systems would be an underestimate. Direct air capture literally extracts carbon from the air to sequester underground, which provides an upper bound on the cost of carbon. Climeworks says it only costs around $600/tonne today[2], with them and various startups claiming they can get it down to $100-$200 in the future. Taking all those numbers into account, here's how much airline fares would increase if carbon cost is factored in:
cheap ETS ($10): 1.5%
expensive ETS ($100): 15%
future DAC ($200): 31%
current DAC: ($600): 92%
Of course this doesn't factor in the cost of the electricity used to power the trains, which would at least partially be from carbon emitting sources. Given that, and the fact that building high speed rail is fraught with uncertainty and cost overruns, the highest fare increase you could plausibly argue for is the "future DAC" figure. This may be enough to advocate for banning air travel for short to medium length journeys, but I doubt long haul flights are going anywhere.
i wonder how this comparison would shake out if you included a carbon tax that effectively measured the cost of these trips on the globe.