For another example, Bombardier in Canada was a successful airplane manufacturer, and the demands of its unions gradually sapped its international competitiveness.
For yet another example, all the passenger rail services in the US went bankrupt after they were forced into collective bargaining with unions.
It's common sense that unions, backed by laws that give them an extra-contractual monopoly over who a company can negotiate with, are not good for industry.
If they were, shareholders would push for their companies to have their workforces unionized. The only reason the notion that unions are good for the economy has any traction is that there are millions of parties with a conflict of interest in this debate, who use their time to push these pro-union-monopoly talking points.