When airline passengers fly between big airports on major airlines, they pay a per-ticket tax to the federal government for the privilege. But when the same passengers fly on commuter airlines into any one of 153 small airports in 35 states and Puerto Rico, taxpayers chip in to pay them, too.

Such small airlines and airports get $188 million a year in subsidies, an amount that has grown from $50 million a decade ago in a program that was only projected to last 10 years, but now has no ending date.

Four airports in Maine benefit from the program: The per-passenger subsidy is $98 for Rockland, $100 for Bar Harbor, $109 for Presque Isle and $129 for Augusta.

In other parts of the country, where passengers are more scarce, the payment can run several thousand dollars per occupied seat.

That has led fiscal conservatives in Washington to question the value of the program, wondering why people can’t pay full freight for their trips.

Airports and airlines reply that if they did charge the full cost, most people would either pick another means of transport or find another place to vacation or do business.

Sen. Olympia Snowe says ending the support would have a “crippling effect” on commuters and would halt or reverse economic development in rural areas of Maine and the nation.

While the free-market argument is an attractive one, critics should recall that there are no means of transportation that do not receive some sort of public subsidy.

Fuel taxes pay for highways, other revenues keep railroads going, and airlines benefit from a wide range of aid, from runway paving to air controllers, that keep airports open.

As subsidies go, $188 million for 153 sites isn’t that much to complain about. Pork-busters have much bigger targets to aim at if they wish.