Unions have their place for protecting some workers, though very few modern workers actually need anything in the way of Union support (there's a reason unions are dying). But you cannot use history as a reason for keeping unions. A lot has changed in management philosophy in 100 years. Workers are viewed less and less as expendable commodities and more and more like valuable contributors (at least those that deserve to be). If unions truely were the way to go, the hundreds of great non-Union companies that litter "Best places to work" lists in business magazines everywhere would not exist.
With regards to the Airline industry. While unions certainly were a major factor in the demise of several major powers, the companies themselves were the ones who agreed to many of the laughable salary/status structures, etc. To that end, let the unions, whom workers tend to follow blindly like lambs to slaughter, and their corporate counterparts fall. Then, from the ashes, more companies like SouthWest (not necessarily the business model of low-cost, low-service differentiation, but of management philosophy of celebrating the employee) will spring up.
I have found that Unions tend to benefit the Union leaders and select undeserving individuals. By undeserving individual, I am speaking of the worker who doens't perform his job in a satisfactory manner yet keeps it due to Union power (If you have ever worked in a GM auto plant, you've met this guy). The deserving individual, who would likely garner more wages outside of a union system, is the one who pays. There are many instances of non-Union employees making considerably more than their Union-tied fellow employees while doing the same job for the same company
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But Unions do bring some workers together and pacify others and for that I applaud them. But common sense would tell you in this modern era of business, they are generally counterproductive.