Subsidies for airports, airlines, FAA, etc. have noting to do with what the nation should spend on Amtrak and passenger rail.
If passenger rail is a good investment, which it is in some corridors, the monies will be found for it. If it had the potential to generate a return, private investors would put up the money. They have for bus companies, airlines, cruise ship lines, freight railroads, trucking companies, etc.
The Pension Benefit Guaranty Corporation (PBGC) is a quasi-government insurance company. It collects insurance premiums from the participants. When a company terminates its qualified pension plan, it is simply cashing in its insurance policy. I reviewed PBGC’s financial statements about a year ago. It had not used taxpayer monies to cover its liabilities at that time, although it is underfunded. If it cannot make up the difference, the taxpayers could be on the hook for the variance, but it is unlikely.
Where is the evidence that outsourced work performed by the airlines is done by workers whose compensation packages place them below the poverty line?
A number of studies have shown that air travel today, when adjusted for inflation, is less expensive than was the case before the airlines were deregulated.
Where the money comes from can be traced for any legitimate activity via an audit trail. This is true for Amtrak, FAA, Aviation Trust Fund, Highway Trust Fund, etc. It is more difficult in the case of fraud, but in most of these instances forensic auditors (investigators) will find it. There is nothing mysterious about it if one knows where to look for the data and takes the time to do so.
Determining whether costs have been accounted for properly is another matter. All cost accounting models involved some allocations, as per another post, and allocations frequently give rise to disagreements.