It is very difficult to compare subsidies: what to count, what to leave out, how to make comparisons in levels of service and point to point totals. Air travel should include airport development, the FAA, subsidies and tax breaks to manufactureres, huge security costs, construction of roads and transit to airports, etc. Arguably it should include the 8 pounds of climate changing CO2 emitted per pound of fuel burnt and the protection cost and risks of importing all that foreign oil.
My original point was that the world is running out of cheap oil and the dependability of supply lines is decreasing. Air travel bloomed in an age of $10 a barrel oil, at $100 a barrel it starts to have real problems and at $150 may be non viable. So arguing over the exact subsidy split may be besides the point - either we have an alternative way to travel at reasonable speed using domestic energy or we don’t. Given that there is no time advantage under 500 miles (and a considerable nuisance cost) we would be well advised to invest in our corridor trains and discourage short flights. It should be a national security priority.
The discussion of downtown depots should include the fact that trains can stop at suburban stations on both sides, planes can’t. Parking at these locations is far cheaper than downtown or airport. The important thing is to have that integrated transportation system that is sustainable well into the high cost energy future.