"Are Amtrak subsidies equivalent to the monies used to prevent the commercial airlines from going belly up after 9/11? If the government pays to maintain private air transportation companies, why not rail?" [via Cox Crow]

Good question. Other than that (logical answer) airlines serve more people or that (cynical answer) airlines have more money, better lawyers and lobbyists, I'm not sure.

Regardless, I can't think of a better transportation investment than a national rail network.