I am mixed about Unions.
I have been in the Union and if I had stayed in it, I would still be at my previous job, making over $20 an hour. I lost my Union membership when I took a promotion and was terminated "at will" a few months after.
They do offer protection from the whole "at will" employment, which means a company can fire you at anytime, for any reason.
They also protect workers who are pieces of garbage. I saw an employee sleeping in the break room once, while his flight was on the ground. The Supervisor asked him to wake up and go out to his flight. He told the Supervisor off and proceeded to sleep. They fired him on the spot. About a month or two later, the employee was back on the job with all the pay he had lost while terminated. That is not right.
The number one issue is pay. The company does not pay you out of the goodness in their hearts and a Union will surely get you better pay and benefits.
Overall, I like Unions. However, I believe they are a dying breed.