I've worked in two aerospace companies that were unionized - the first a very well-run company in California, the second a passably well-run company in Texas.
The Unions were a constant impediment to improving product quality and production rate (and for aircraft, quality is exactly equal to safety!), even when there was no automation involved.
The first company invested in a robot to process parts by blowing hot air through them so adhesive didn't bridge over the perforated holes in the part. The union objected, and a $100K robot was reduced to being a heat gun holder for the union worker that now manually processed the part just as before, with a huge scrap rate, since touching the part with the heat gun ruined it.
Despite the company working hard to foster good relations with the union, the union decided to strike not for any work demands, but simply because they had money built up in their strike fund. A couple of weeks of violent protests (burned cop cars, etc.), shots fired at engineers (including me) stationed as lookouts on roofs to prevent arson, etc. convinced me that unions are never, ever better than thuggish extortionists.
Since those two (my first jobs) I have refused to work for any company with a union. And I'm back in Texas, a right-to-work state where union membership cannot be compelled even if a company is unionized.
I have NOTHING good to say about any experience I've ever had with labor unions. They are bad through and through.