"Are Interstate Highways and their ongoing improvements welfare for trucking companies?"


It's not analogous, since we all use the highways and the government is not giving money directly to trucking companies. Airlines have similarly benefited from taxpayer money spent on airports.


"The government has a role in the economy to provide for services and facilities that the private enterprise can't provide for themselves."


True, such as protection from terrorist attack. However, the federal government has gone far beyond providing essential services that private enterprise is unable to provide.


"Is the airline industry vital to our economy? I would think so."


Are you suggesting that the industry would cease to exist if they don't receive welfare? Why can't they respond to changing market conditions like other businesses by down-scaling, cost-cutting, merging, increasing efficiency, raising prices, etc? Free market economies usually find a way to fulfill vital needs.