If I ever was forced to join a union, I'd quit on the spot and go find somewhere else to work. I worked for Comair (small airline owned by Delta) during a stewardess strike, which ultimately caused the company to sell planes and eventually go out of business. Big unions like the teamsters don't give a crap about their members, only their power and greed.
It was said a year or so later that the teamsters were talking to other airlines saying, "Don't give us what we want and we'll pull a Comair on you". All of the Stewardess union members, airplane mechanics union members, and pilots union members were furloughed aka given indefinite non-paid leave due to the profit imbalance that the highest paid stewardesses in the industry caused on a sub-par airline.
No thanks unions. There is enough free market for what we do that they aren't necessary.