Traditionally, targeting
Traditionally, targeting older workers for early retirement packages is used to give incentive for the higher wage earners in a company to leave and make room for younger, less experienced and cheaper workers. Every company does it.
Caterpillar, for instance, has been giving incentives to older workers to retire early and closing down plants in high-wage (generally unionized) areas in order to move to younger, less costly workers in other areas. They recently shuttered a Canadian plant and are now opening its replacement in the southern U.S. (don't recall the state).
Manufacturers are tired of battling unions and always losing. In large part, GM's continual losing to UAW is the reason that company ultimately failed (and got bailed out). Ford had to threaten death in order to break the unions of their "give us everything" demands. I'm sure Chrysler was in the same boat as the others. The railroads are heavily subsidized and are, coincidentally, also heavily unionized.
Labor is like any other commodity. Those buying it will find the lowest-cost, but most skilled options they can. Those selling it must make themselves competitive by either offering a lot of benefit or lowering their price, just as businesses do to sell products. This is true no matter the industry, no matter the product, no matter the business type.
I've personally been involved in this process multiple times, usually from the labor end of the deal. I didn't complain when I was found to be less useful than a cheaper worker, I just moved on to something else. Adapt, survive, thrive.
It's how markets work.